There are advantages to distributed infrastructure as well! You mentioned one of the biggest disadvantages.
I am thinking along the line of:
- You can just do it / upgrade it etc
- Robust against central failures for various reasons
- Resistant to those in charge of centralized infrastructure abusing their monopoly
Utility solar is also distributed if there is enough of it installed to matter for discussion. A single installation is such a tiny share of the electric load that we can ignore if for all reasons you care about distributed. (or care about solar for that matter - it is a drop in the ocean for the environment)
Utility-scale solar might be cheaper but doesn't make my house resilient to grid failures. It also only benefits me when the grid is upgraded enough that ... well, it benefits me.
Utility companies are not incentivized to lower prices because it means less money for them. Do you remember when power companies told people to conserve power and then people successfully did this? And then they raised rates because they weren't making enough money? This happens in California ALL THE TIME. I've lived here 30 years in Silicon Valley and it's the biggest scam that no one talks about. It happens with electricity and water. With water its even more egregious because they told us to conserve water because of the "drought" but once the drought was over, they raised rates because people weren't using enough water. My connection fee to water is over $100/month without spending a drop of water. That's why I stopped conserving water and water my lawn every single day because it turns out that my water costs are only about 1/3 of the actual water bill costs so fuck it!
It's the same playbook over and over again, there's no incentive to lower rates at all because it's an easy way to make money over an entire population of tens of millions of people.
Now PG&E is fighting to charge solar panel owners $100+/month just for the privilege of being connected to the grid. That would make having solar panels even more expensive than not having solar panels which is utter hypocrisy but no one seems to care or point this out. It's a complete and utter scam.
I live in Florida, and I'm building a water battery, so I can freeze it at night when electricity rates are cheap, and use it to cool the house during the day.
The day after the system goes live, they'll probably announce flat rates for any time of day, just to f' with me. :(
You wouldn't happen to be sharing this builds information publicly would you? I can fully respect however if you are not.
I am a staunch DIY serial entrepreneur techie that has used my grey goo to build and sell a few companies and my time now is spent similar to yours although using a different application of physics. I too am motivated, just as you are, in my efforts to apply what I know to further reduce my energy costs which will not stop rising for quite some time.
You really made my day with this post and I hope we can find more folks like ourselves from your share because in time 'dogfooding' new ideas at home will lead to new applicable discoveries for all.
> The day after the system goes live, they'll probably announce flat rates for any time of day, just to f' with me. :(
Every system like yours works to flatten the prices, but it looks like a pretty big swing between peak and off peak pricing today, so it'll probably be a while before flat pricing again.
18.8% Nuclear and 8.4% solar (more than double the national average!)
OUC on the other hand has less than 3% Nuclear (generated / purchased from FPLs plant on Hutchinson Islans!) and <6% solar, with a massive 24% still being generated by coal! (FPL demolished their last coal plant ~8 years ago in Indiantown, I watched it live!)
So while FPL is technically for profit and OUC is not... FPL is cheaper and greener than OUC.
I say this as a long time Florida resident who remembers when FPL truly sucked in many ways. They’ve, demonstrably, put in effort to make electricity greener and cheaper here in FL. (Even with all of their efforts against home solar).
It is easier to find a million people with a few hundred euros and a sunny balcony than finding one dude with a few hundred million euros and land on which building a solar farm is permitted.
Where I live we have Time of Day electricity pricing where the prices jump 2-3x during high demand. Panels conveniently produce the most power around this time, so this can save people money.
Isn’t it backwards? If everyone had a little bit of home generated power, then the actual energy part of the bill becomes smaller, and the cost of transmission becomes an even greater fraction of the total cost.
And since transmission cost is typically bundled with the energy cost, it means the final retail energy price has to go up to cover the transmission cost.
With less energy drawn over the wire, the transmission cost goes down since less transmission infrastructure being used. The overall transmission cost should go down as well since there's less need to expand the transmission infrastructure.
NW florida just had a hurricane. As I type this comment there are hundreds of thousands of people in the sunshine state that have no (grid scale) solar power. That from a heavily solar provider. All of my friends report that (largely) trees are down but houses and roofs are okay. Distributed solar would have a lot more people with working refrigerators and unspoiled food.
You don't even need distributed solar. A simple UPS is enough, either plugged in in front of the refrigerator or wired to the entire home via a transfer switch... and hell it's not that expensive. Battery stations capable of feeding a refrigerator for a day are less than a grand, if you don't want batteries a gas-powered generator is even cheaper.
Just how many natural disasters do Americans go through before realizing that?!
Hurricanes a much bigger natural disasters then you think. Several weeks without power isn't unheard of. The battery that runs your fridge for a day will be dead before the weather clears up enough that it is safe for workers to attempt to restore power.
These disasters are rare though for any one person - a few happen every year, but it will be years between you personally seeing a disaster. That is why generators sell out when there is a storm: even if you have a generator odds are it is rusted and won't work. It is a waste of money to buy a generator before you need it.
> Just how many natural disasters do Americans go through before realizing that?!
This is one of the most condescendingly-wrong posts I've ever seen on this site and you should be embarassed for writing it. The beginning was just typical hn hubris that I probably wouldn't have responded to, but that last jab at the end in the context of an active and ongoing emergency that you clearly know nothing about is completely insensitive and gross.
Having traveled to those areas many times to assist with recovery, slept in trucks for weeks, and made many friends in those areas: It's day four without power and that is not abnormal. Bigger storms you can go weeks without power. Batteries aren't gonna cut it.
And gas generators have a whole mess of problems.
- Gas doesn't store well. Your stored gas is gonna go bad. That means when you find out a hurricane is coming to your area you can spend your time either protecting your house or wait 3-6 hours in line to hopefully get some gas for your generator before it runs out. Maybe they are rationing to 5-10 gallons.
- They might not work after sitting for years, even when properly maintained (one of my friends had two and neither could get running even with help). Hurricane areas are humid: generators rust. If you don't use gas engines the seals dryrot. If you leave them sitting with gas in them the ethanol (sugar!) Separates out and gums it up, breaking your generator. If you stop using your generator in the wrong way then you'll break it (you need to run it dry, using/wasting all the gas in the tank).
Even if you score gas and your generator works that brings us to the next problem:
The gas stations can't pump gas if they have no power themselves. They also can't be refilled if the big gas tankers can't reach them due to trees blocking roads. Main roads become passable quickly, side roads might not work for weeks. Cell phones might be out for weeks (and modern 5g micro-sites will take even longer to get fully rebuilt across a whole county). If your close-by station can't get gas you can't just call around to fine somewhere that does. You can't just drive around either. Single lane roads mean going anywhere takes forever and you are actively hindering recovery efforts. There are still stations in florida unable to pump gas due to shortages or power loss. So your couple of gas cans got you through a couple of days, what now?
And gas generators have moving parts. They are complicated. Another friend there had theirs die the day after the hurricane. Shit happens.
There is a reason prevalence of gas geberators in hurricane areas is less than 5% (I probably hear one running for every 50 houses, but most run them only intermittently) and it isn't because they're just dumb hicks who aren't as smart as mschuster91.
Lastly, you need to know how to use one. Every time there's a hurricane someone puts it in their garage and poisons themself and their family to death. Should you know better? Yes. But everyone doesnt.
Then there's all the other ways you suddenly need to spend energy to survive: you need to boil water, sometimes for weeks (while you don't have power), you need gas for your chainsaw to clear roads/trees so that power and water can be brought back. You need to drive to get supplies. Wasting gas that could be used to recover from the disaster isn't wise.
Back on topic: A stack of solar panels that could plug into the same outlet as a fridge would be a godsend for a lot of people (while also storing better than a generator and being more compact -- so more can be trucked in after a disaster.)
With a much higher capital and regulatory hurdle. By individuals self motivated to reduce their own costs with their own small capital investment you get a power source that’s crowd sourced. It doesn’t have to be as efficient to be more effective.
The biggest problem with plugging a generator into an outlet is you need a double ended cord. If you use everything correctly they work fine, but there are too many ways things can go wrong. The most obvious one is you plug everything in, start the generator, and the trip over the cord on you way back inside, thus sending the live male end flying toward you. Once in a while a kid will see these dual male plugs and plug them in - lots of ways things can go wrong here.
There is also the problem of backfeeding, but this is more theoretical - even if you know to limit your power use, your neighbors won't and so your generator will trip its own breaker. Linemen are taught to either treat power lines like they are live, or to short them to ground - it can happen they don't do this and you kill a linemen, but still not as big a worry as it is made out.
They make generator "inlets" that sidestep all these problems when used correctly. Most common I've seen is a block so you can't have the inlet and the main breaker both on at once.
> There is also the problem of backfeeding, but this is more theoretical
it is not theoretical from the POV of power company employees working on their lines. the power goes out, they go to fix the equipment or wiring, and if the inverters connected to the grid have not shutdown, there could be 10s of kW to even MWs being backfed into the system they are working on.
that's why in the US at least, grid-tied inverters are required to have protection against this. if they do not see power from the grid, they shutdown (and rather quickly).
Hang on. You didn't address the reason they gave in the half sentence your quote skipped. How are those backfeeders going to keep going when there's way way more load than they can possibly supply?
> if they do not see power from the grid, they shutdown
I realize this is a complete noob question but I'm still curious: with enough "backfeeders" could it not in theory be possible that the backeeders see each other's output and keep operating?
Say, a few houses at the end of the line, each with very little electricity consumption (no-one's at home), but with panels and inverters going full tilt, something like that?
Apparently the anti-islanding features in the inverters prevent this kind of situation. They need several minutes of clean power to start back up, and do other checks.
Yes, this is a concern with some older inverter designs. They use phase-locked loops which are meant to lock to the grid frequency but if you and your neighbours on the feeder are generating and consuming a roughly equal amount of energy and the feeder loses its connection to the wider grid, the loops can lock to each other and form a stable island. How long this would last in practice is not really known, it would probably be rare for it to happen at all and even rarer to stay stable for more than a few minutes but it has been demonstrated so it could have become an issue. Newer inverter have specific anti-islanding protection to detect situations like this and disconnect if it happens.
(the specific case of very little consumption but panels and inverters going full tilt doesn't work as this would lead to the frequency rapidly increasing, exceeding inverter set points and the local grid collapsing with all the inverter tripping off. The danger scenario is closely matched load and generation, like a real grid)
Thanks, anti-islanding protection must be a fascinating topic. You could look for voltage, frequency, phase anomalies but you also have to balance between being safe and having too many false positives. I'm not sure I'd want to be a line worker knowing there may be many inverters, from various manufacturers and with varying levels of quality, in every direction.
Perhaps a more robust solution would be for the power company to install remote-switchable circuit breakers at various places of the grid. Use some sort of wireless IoT protocol to listen for "on/off" signals and to report back "I'm now on / I'm now off!". Then the power company can disconnect parts of the network by themselves, without trusting that every inverter, generator and battery will do the right thing.
Again, all linemen are taught to short the wires or they are alive. All grids have regular places where two different lines meet and there is a switch at those points where in the worst case is they can cut the down line close a switch that normally is open and they can back feed a line from a different one and get power to people who are on each side of the break and then they can come back later to fix the break. These switches are miles apart, which means that you cannot be sure while you're working on the line someone else didn't go to that switch and change it.
Also, people have been back peeking the grid from their home generators for decades by now. Solar and inverters are a different variation of that attack, but it is nothing new. Any utility will have procedures because they can't guarantee that's not happening and we learned years ago.
I'm not saying it never happens, only that correct procedure already makes it not an issue
The back feeding problem is actually identical for plug-in and regular inverters. When the grid goes down, they keep generating power, creating a disconnected 'island'. All inverters are designed to be incredibly unstable in this mode, quickly desynchronizing from each other.
tl;dr Plug-in solar inverters must power off within a second if they stop detecting the grid's sine wave.
Generators have no such protection and will happily backfeed through the transformer outside your house to energize power lines. Line workers are careful, but there have been deaths. After hurricanes seems the most common based on a quick search.
So it's not a stupid question, indeed you should never plug a generator into an outlet. The double-ended "suicide cord" which allows you to do that has that name for a reason. (It can be fine to plug a generator into an inlet circuit, if the electrical panel has a proper interlock that physically forces disconnect from the utility before connecting the generator inlet.)
Yep, if you're gonna redneck the generator after a hurricane, you'd wanna disconnect your house from the grid. One trick in more rural areas is to have your power meter hooked up to one panel, and then your house panel be a "sub panel" to this main panel. Now you can shutdown your main panel and still redneck your house.
The better way (and legal way) to do this is to have a generator plug plug installed, this way when you switch over to generator your property is disconnected from the grid.
Generators are synchronous machines which means they can produce a useful reference frequency without any external source as long as they are spinning at a reasonably correct RPM. This RPM is easy to enforce with mechanical means. This independent operation is also what makes them so dangerous. There is no control signal from the grid back to the generator.
It can be quite safe to plug a generator into an outlet if you take precautions to properly island the system. I had an interlock on my breaker panel that would let me turn on a 50A backfeed breaker if my main breaker was switched off.
Generators are typically grid-forming. They can (and will) be out of phase with the grid power, and will backfeed and create hazardous conditions upstream if the grid is out (and your main breaker is still on.) To use a generator safely you need a transfer switch (or similar) to make sure only one source of power can be active at a time.
Solar inverters (esp for this use, but also in general) are grid following; they'll use the existing frequency and support it, and if the grid goes off they'll go off too and do no power-off backfeeding.
The inverters are thus broadly safer to be plugged in to systems that are otherwise unprepared.
Generators could be made grid-following (many are now inverter-based), but for most users that would be silly, since the supplemental power would be more expensive (and louder!) than from the grid.
How do these work when plugged in to only one of the split phases on a US-style 120 system? Because I'm a nerd, I know which legs of the phase go to which outlet in my house, but I don't expect everyone to pay attention to that. I assume something has to take that into account somewhere.
There is no problem and so nothing needs to account for it. A split phase is just a transformer with three windings, and one is connected to the other. We call one side (high voltage) the primary, and the other two secondary, but the transformer doesn't care at all, it can send power either way (there are limits but we are well under the maximum rating of the transformer so we can ignore them). If you only draw 240 volts then the two connected windings act as a single secondary, if you only draw 120 then one of the two secondaries provides power. Any other combination - the transformer doesn't care.
The electricity from the plug-in outlet is consumed by any devices connected on the same circuit first. Any excessive electricity is fed to the circuit breaker panel’s bar connecting all circuits on the same 120V split phase; the devices connected the the circuits on the same split phase can use the plug-in electricity next. Any excessive electricity is fed back out of the meter on the 120V split phase line on your main service connection, then to the electric company’s transformer at the street block. The transformer might feed it to your neighbors. In any case the transformer feed electricity to the other 120V split phase line back into your service connection, the meter, the panel, the other split phase bar, the circuits on it, and the outlets on them. The devices on the other split phase circuits technically are not using the plug-in power.
Most modern meters will debit and credit the electricity going in and out on both split phase lines as net meter, so the electricity consumed in the other split phase is counted as consuming the plug-in power. However some old meters add the outgoing electricity up as consumption so you are paying for the electricity fed into the grid. Call your utility company to make sure.
Also, unless you have a net metering agreement with your utility company, you won’t get paid for any excessive electricity fed back into the grid.
Solar panels are getting cheap enough for grid hook-ups, installation and regulatory approval to become the bottlenecks.
Plug-in solar is suboptimal in many ways, but it does sidestep a lot of those hurdles. Not too surprised to see it on the rise.
Another thing that might be worth keeping in mind is that plug-in solar panels are often installed vertically - i.e. balcony solar. In which case the peak of the panel's generation is offset to the edge of the typical "duck curve". If it gets popular enough to affect the grid, it might get the solar-induced demand slump larger, but make the edges even sharper.
Would that make grid scale battery storage with its instant response even more important?
The plug in solar systems are small and usually mounted in ways that don’t capture as much energy as the same panels mounted on a roof. These systems aren’t going to get popular enough to make a big difference in anything.
I think it’s nice that they’re available for people to do some small scale offsets, but I think they’re more of a gateway to better solar installations. They also send people down the path of investigating battery storage add-ons, which might actually be a better long term solution for everyone.
If we can get to a point where we can buy plug-in batteries that are subsidized by requiring coordination with the grid, the power companies could get distributed, controlled battery storage to work with their demand curves. This can already happen with the bigger permanent install batteries.
With the plugin solar I can imagine people in single family residential installing them on both sides of fences and gates to get an around the day benefit.
Also, with the price of solar panels decreasing below most (wood?) building materials with way higher durability, no paint required, why wouldn't it replace most sun facing siding applications aside from being "ugly".
I hope the next step for this is plug-in battery storage. All the on-grid battery hybrid inverters I can find in the USA are either single leg 120V or 12kW for $5k. I just want like 3kW dual-leg with support for a dozen kWh of batteries
Yeah it seems like the inverter manufacturers don't see demand for that. I was thinking maybe the Victron Multiplus-II 2x120 could be paired for 240V output but I was wrong, that's only on grid power, it won't make 240V from battery.
Obviously the inverters and pairing technology exist, but I don't know where to buy one retail.
Victron devices on sale in Europe/UK all do 240V output. I've seen someone do a boat build in the USA with Victron hardware that included 240V circuits (because the builder was a UK/US person, and they wanted both 120 and 240 "normal" circuits).
Yeah you can use a Victron 230V inverter along with an Autotransformer to get split phase 240V. Also, I was sort-of mistaken in my earlier comment but can no longer edit it. The MultiPlus II 2x120 cannot make split phase 240V on battery, but I see that the regular MultiPlus II can be paired to do exactly that. About $2K for a setup capable of 240V 20A. Not inexpensive, but it is Victron, which is amongst the best.
I've seen setups where they put a 48v battery between the solar panels and plug-in micro inverter. No idea how this impacts efficiency or if there's any safety concerns though.
Perhaps also useful would be plug in batteries, especially if one has variable rates. Charge when cheap, discharge when expensive.
One constraint on these I've read is that if you have sources and sinks on the same circuit, you might overload the line without tripping the breaker at the box. If I'm understanding this correctly this has caused them to limit the power of plug-in solar to a fraction of what a single circuit could potentially carry.
Yes, it's designed so that total current and potential heat problems are still within safety margins of circuits built according to code. In most of Europe, one regular (or upper end of regular, depending on country) residential circuit can supply 3.6 kW (230 V * 16 A = 3680 W), so 800 W are "just" a 20% overload.
Problem with this idea is batteries on grid scale are always cheaper per MWh, so grid scale battery operators will eat away any arbitrage you could earn with more expensive consumer gear.
There's not sufficient grid scale capacity yet, there are lots of consumers arbitraging in the UK.
My electricity supplier sends me a message nearly every week saying if I use less electricity during peak demand times then I get free power at weekends. https://octopus.energy/saving-sessions/
I've been doing this as well! It's always 6pm-7pm for me which is when my Cosy tariff has the peak rate anyway, which I try to not use. So for no behaviour change I normally get 1-2hrs of free electricity on a Sunday morning! I got 15kWh for free this week by having the immersion, heat pump, washing machine and tumble dryer running. Not bad for 0 effort on my part.
I'm not trying to make money here though. I'm trying to recoup some of my costs for a home backup for when the grid fails. My house automatically switches to a backup generator when the power goes out, but it is from the 1970s and wearing out, a battery system that can recoup some of the costs by arbitrage is useful even if it loses money.
While the power doesn't go out often, it is a big deal when it happens and so a backup is useful. I'm still fixing the damage from the last one - the sump pumps not running for an hour in a rain storm is expensive. Fortunately it wasn't a long outage, much longer and the fridge/freezer would be a problem. In cold weather the furnace is important to keep running. There are other essential things as well that my house cannot survive without. Beyond that I want my computers to keep running if possible.
My sump pump hadn't run at all to my knowledge (I hear it so I think I'd know but maybe I was always gone or sleeping) for several years, but the power went out in a big rain storm and so the one time I needed it, it didn't run. (my old generator didn't kick on like it is supposed to, but I'm not sure if that circuit is wired to the generator anyway)
Does this seem like a bad idea from a safety perspective?
With fixed solar installs you're likely to find some kind of switch or labeled breaker to disconnect. The system is designed with a central "power in" that's (hopefully) obvious when you're standing in the breaker room.
These things could be injecting power anywhere, so you need to know they're there (which may be less apparent than roof/field panels) and go around and pull the plug(s). Relevant to electricians, firefighters, etc.
Yes, there are serious safety concerns. Both islanding, which is where a circuit is hot when it shouldn't be, and from a circuit overload.
Your circuit breaker protects your circuits by putting all the load (eg your microwave) on one side, and your supply (mains power) on the other. If too much load is present, the circuit breaker trips.
However, plugin solar puts invisible supply on the load side, which your circuit breaker cannot see. Let's make an absurd example so you can see what the problem is, then scale it back.
Imagine someone buys 5 panels that can each supply 5amps. They plug them into outlets on a 40 amp circuit. They then proceed to run their toaster, microwave, vacuum, and hair dryer. They can draw 65 amps through the wires before the circuit breaker trips. (40 from mains, 25 from the panels)
Let's say they had a good electrician who installed 6AWG wiring on that circuit, which is rated for 50 amps. The circuit breaker used to trip at 40, so no problem. But now up to 65 can go across the wires and suddenly you are exceeding rating for wires.
Now you might say, "most of these are 3.5 watts, and they clearly say don't use more than one". But I say that's a "good intentions solution". We should make it mechanically impossible to do the wrong thing. Maybe these panels could try to communicate over the electrical wires, and if they detect a signal from another panel they should self limit. Maybe we need to rethink circuit panel design. But as it stands people will absolutely buy one of these, decide they love it, and then buy 4 more.
In the original example, RCD/circuit protection is regulated on the _property_ side, e.g UK has EICR for electrical install. Once its done for a property, its good until next inspection (in theory)
This moves the protection to the _appliance_ , which while it needs to meet certification, is much harder to police a consumer electronic device, than a physical unmovable premise.
I think these are great, but there will inevitably be devices that don't implement the spec correctly that still get sold to willful or unwillful consumers that result in danger to everyone.
I think this is probably fine, since UK circuits are typically 20A. Apart from fault current (which would have to be line to line, since line to ground would trip the RCD), it's quite hard to end up with more than 20A of stuff plugged into regular sockets unless you're overinvested in portable heaters. All the big stuff - cookers, heat pumps, showers - is on separate breakers from the sockets.
> Imagine someone buys 5 panels that can each supply 5amps. They plug them into outlets on a 40 amp circuit. They then proceed to run their toaster, microwave, vacuum, and hair dryer. They can draw 65 amps through the wires before the circuit breaker trips. (40 from mains, 25 from the panels)
Circuit breakers trip bidirectionally, so the circuit breaker itself would protect if too much current is drawn through to the mains panel.
How, precisely, would you get 65A through the wiring on this 40A circuit, if I drew 40A of consumption and had 25A of supply?
The 25A cancels out the 40A, so the upstream feed would only see 15A total. You do get 65A of total current drawn through the breaker panel, which is a concern, but the supply wiring would not see 65A. Subpanels (which, this would be a subpanel if it only had 40A capacity) are typically going to be just fine.
In the UK you typically make a ring circuit. In the US you make branching circuits.
In the US you get: Mains -> Breaker -> Outlet 1 -> Outlet 2 -> Outlet 3.
In the UK you get: Mains -> Breaker -> all outlets -> Breaker
In the US, assume I had 65A of load on outlet 3 -- I've plugged in too many things into a surge protector. Assume a bunch of solar panels are on outlet 1.
The the diagram looks like: Mains -40A-> Breaker -40A-> Outlet 1 -65A-> Outlet 2 -65A-> Outlet 3
Now, the breaker won't trip because only 40A are crossing the breaker. But 65A are on the wire between outlet 1 and 2 and between 2 and 3.
My concern is what happens to grid stability as we replace synchronous generators, with their enormous rotational inertia, with thousands of grid-following inverters. They can all phase-lock to 60 Hz, but without enough inertia, what keeps that frequency stable during sudden changes in load or generation?
Synthetic inertia. Essentially, loads that you can quickly either shed or bring on in response to fluctuations. There can be a market for that too and that's what many grids are slowly discovering.
There are still a lot of synchronous motors out there directly wired that provide real inertia. Though these two are moving to VFDs (which are cheap and variable speed). Still I expect battery backup systems will come online more than fast enough to replaces the losses.
> The system tripped his apartment’s circuit breaker and shut off his computer several times, but a different inverter solved the problem.
I think this will be your biggest practical issue in newer US construction. Arc fault circuit interrupters are now code for any wiring in living spaces. They can be quite sensitive to weird switching loads (and sources). I was forced to swap an AFCI for a normal breaker in my last home. The power supply in my workstation triggered the detection heuristic in the AFCI about once a day. I could cause an outage on demand by running certain workloads.
I really don't understand why most people here act like this is some weird unproven and unsafe technology. This is literally a solved problem. They are everywhere in Germany and it's no issue.
The inverters follow the grid AC and shut off their output if they are disconnected or unplugged, so the plug is never "hot". The power they input into your home wiring/ the power grid is limited to 800Watts to not overload any installation. And the power meters know not to run backwards if you happen to feed power into the grid.
If you want, you can add battery storage that follow the same rules but let you save excess power during the day to feed into your home at night or during demand spikes (washing machine, ...).
The setups are dirt cheap and pay for themselves in about 1-3 years in saved electricity costs
For panels and inverters, there's really too many to count, but mostly names that one is not typically familiar with. For integrated solutions, familiar names might for example be Anker Solix or Tepto, which offer battery storage with integrated AC inverters. I'm running an Anker Solix Solarbank 2 E1600, which is not really the latest model but rather cheap and runs nicely.
If you want to get an overview of the ecosystem, googling "Balkonkraftwerk" gives you the most relevant results.
Essentially this is simply what solar panels have done for ages, feed back electricity to the grid, sure it's not through a power outlet but essentially it connects to the grid in a similar way.
What's new is cheap and ubiquitous micro-inverters. Before it wasn't worth putting a $800 inverter on a small 2-panel 600 or 800 installation. Now with micro inverters being so cheap, this tech becomes viable. And with loads so limited (less than a microwave) the regulation is equally light to allow this convenient plug-in solution.
You might be thinking about it as you might a DC circuit or a battery with electron shuffling one-way down the wire.
But it’s AC, the electrons are shuffling in both directions at 50/60hz
Voltage goes forwards and backwards and odd but current also goes forwards and backwards, for both appliances and generators.
The difference between consumer and producer is only the phase angle between the voltage and current waveform.
Because power is VxA, do that across the wave cycle and the power direction changes for consumers and producers.
At every junction, Kirchhoff’s current law will sum the currents so you get a “net current” waveform on a wire that might have both a kettle and a plug in solar panel.
That summation means the kettle will chomp as much current as the panel can deliver and than take more from the grid. Swap the kettle for a small LED which takes a fraction of the current and the sum gives a NET supply, and on to the next junction.
Maybe a useful mental model is a trampoline? The grid is like a jumping elephant or something (I don't know if they jump, we'll say they do for the sake of the analogy), and you could have people also jumping on the trampoline. If they're a bit late, the elephant launches them in the air, and if they're a bit early the elephant sucks the energy out of their jump, but that energy makes the elephant jump higher. And a fully distributed grid would be one where there is no elephant, just a million people jumping on a trampoline.
I think at this scale that it's cleaner to think of the grid as a flywheel system of enormous (~infinite) mass. Every consumer (home, factory, business, whatever) and every producer (home solar, nuke plant, wind machine, whatever) is connected to this flywheel system, and they're all in parallel (just like circuits in a home are).
Take power out of the flywheel? Sure, why not -- that's exactly what we've done with it at home since we had an AC grid to speak of.
Try to impart higher voltage to put power back into the system? Fine, no worries. Flywheel just accepts and absorbs whatever you put into it as long as it fits.
Try to change the flywheel's AC frequency or waveform, though? Hah, fat chance: Flywheel will trip your breakers or reduce your gear to ash -- whichever comes first. We play by the flywheel's rules, and those rules aren't optional at all. It may be just a big dumb flywheel, but the flywheel's enforcement is absolute.
Anyway, it's a big mythical flywheel. We get charged money to take power out of it, and (with the right arrangements) we get paid money to put power into it.
And by design, grid-tied inverters are quite good at following the flywheel's rules. They match the flywheel's waveform very well [lest they go poof]. They can only put power into that flywheel, and they reject power from that flywheel. The inverter is a one-way thing that, from a high-enough viewpoint, looks kind of like a check valve or a diode does.
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But it's not an ideal, perfect system. It does not exist in a world of frictionless pulleys and ropes that don't stretch.
That imperfection shows up in the wires and transformers connecting the house to that flywheel system, in that these parts have a non-zero impedance. (For the sake of this discussion, impedance can mean about the same thing as resistance)
And that impedance is useful. It means that we can increase voltage a very tiny bit on our local leg, and thereby succeed at using our puny little solar power system to help cover our own local base load.
Suppose our plug-in solar widget can produce 800 Watts today. The plug-in kit increases the voltage that it drives that plug with until 800 Watts of power output is achieved (which is only a very tiny amount of extra voltage, but it's real anyway). This is its purpose: Where some robots pass butter, this robot puts 800 Watts into a power socket.
Since the wiring between the plug-in solar and the local household baseload stuff has a lower impedance than the mythical flywheel does, our baseload stuff (the fridge, the router, the fan by the window) gets first dibs at that 800 Watts of minutely-enhanced voltage.
If we produce more than we use, the excess local power production gets provided to and soaked up by the flywheel (maybe we get paid for that).
If we use more than we produce, then the deficit is made up for by the flywheel (and we definitely pay for it).
If our generation and consumption is perfectly balanced (which never really happens), then the flywheel plays no real part in the program except to provide a waveform for our solar inverter to synchronize with.
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Anyway, it's not new tech at all. It's safe in that it won't work at all without a connection to the big flywheel in the sky. And folks have been using grid-tied inverters for quite a long time, but that was done on a dedicated circuit (with a dedicated breaker or fuse or RCBO or whatever they're called wherever you are).
An important new part is that it can be a plug-in system that works without individual planning or permitting: A person can legally buy and use a kit without obtaining extra permission.
Another important thing is the safety of sharing a circuit since enhanced potential exists for overheating things. Germany limits their plug-in solar to 800 Watts, or about 3.5A @ 230V, while their circuits are usually 16A.
That means there could be as much as 19.5A of nominal current flow within a circuit be...
It’s not even really an issue with DC either, like a lot of people’s battery systems have multiple DC loads and multiple sources (e.g. DC MPPT solar controllers) going to a busbar connected directly to the battery.
Current load pulls the voltage down, sourcing current pushes it up. No bother, as long as your sources cut out if the voltage goes too high, and your loads cut out if it goes too low.
Maybe the issue is in the terminology? In the UK, we don't call it an "outlet", we call it a "plug socket", or just "socket"; it's a socket that takes a plug, no direction is implied.
In terms of electricity and physics, this is unremarkable, the bit that probably scares people is the fact that you have a plug connected to something that's _outputting_ AC, particularly for those of us with 240V supplies.
If it were any old AC source on the other end they'd be correct, but current technology allows the output to be cut in milliseconds, faster than the period of a single AC wave, once the plug is removed.
Tangentially; if you have solar (mine's roof-mounted) don't assume that flipping the breaker means there's no power; I live in a 1930s UK home with all sorts of interesting wiring and flipped the breaker to change a plug socket, only to be shocked; literally and figuratively when it was hot.
No, I think it's that we've been repeatedly told of the dangers of plugging a generator into a socket of the house and the problems that will occur if the power comes back on if it's still running.
When we had our solar installed, we had to make sure we had a newer power meter that could handle power both ways, so it probably is a problem for some situations, but the power flow for a single solar panel into a plug isn't enough to trip this, or maybe newer power meters are better?
We definitely think of it as somewhere a power comes out of, but I don't think it's the name, just that it's only ever been that way.
Clearly some people think of it differently if they're plugging generators into wall sockets to power the whole house, dumb as that may be.
There seems to be several levels of compatibility, at least here in the UK, based on age.
My home is 1930s, it's fuse, in the black Bakelite housing typical of the era was insufficient and we were missing a incoming breaker to/from grid, those were updated. Our meter is much more recent, though still dated; allegedly it would have worked but it wasn't a smart meter, which we wanted so we had that updated.
I've also heard through my many hours of watching Solar videos on YT before our install that some breakers, RCDs(?), RCBOs(?), whichever it is, aren't always suitable for bidirectional current flow, so that's a possible issue too.
All of that is aside the "suicide cord" danger of the old generator method, but that's gone now with modern tech, the output is cut before you can get your hands on the contacts on the end of a plug.
It's just been legalised here in the UK, and I think it will help people with their bills, but the key is to keep installation costs down; if it's DIY you can look at a decent ROI time, but with the cost of trades-people these days, if you have to call out a sparky to inspect before you plug it in, you've added potentially years to your payback period.
At ~800W, I think on the whole we'll be fine; the equipment in our homes has got much more efficient over the years, and our homes were mostly built for times where we were using higher powered devices. If you can draw over a kW to power an electric heater or kettle, I don't see why feeding a mere 800W back in would be a huge risk.
Disclaimer: I'm not an Electrician, but I do have a degree in Electronic Engineering.
You can backload via generator plugged in. Nothing physically stopping it. You just would need to shut off the primary breaker so you don't load the line outside of your house.
The solar is the same way, but with an auto cutoff.
> No, I think it's that we've been repeatedly told of the dangers of plugging a generator into a socket of the house and the problems that will occur if the power comes back on if it's still running.
Yes, but that's dangerous for reasons[1] that people often don't bother explaining -- and that aren't important for solar grid-tied inverters[2].
[1]: The seemingly-ideal way to plug a big fat generator into an American house in a hurry is to use a double-ended suicide cord to feed into the 240v dryer outlet. That provides plenty of power to get a lot of things done things, it's a single-outlet circuit, and it lights up both sides of the split phase panel. But that's bad.
The most obvious way that it's bad is because we shouldn't have energized male prongs. Like, ever -- that's just extra shit to get hurt with. But this suicide cord idea relies upon their use.
The other way that it's bad is that the generator doesn't know whether the house is still connected to the grid or not. So unless we deliberately disconnect from the grid, there's a wonderful chance that we feed it even though that grid is presently non-functional. This can fuck people up: The transformer on the pole outside (or in the box down the way, or whatever) will cheerfully convert the sleepy 240v from the generator into thousands of volts on the wires outside that were completely dead until someone decided to get clever. Now, the guy cleaning up storm debris down the block or the lineman doing the repair gets the fuck shocked out of them in spooky-dead kinds of ways. (Yeah, yeah: We shouldn't ever do anything near downed lines of any kind, and the lineman should always have appropriate PPE. And we shouldn't plug our generators into our dryer socket, too. Death is permanent.)
Panels with interlocks and wall-mounted male sockets exist that can accept generator input both exist, and the combination of them mitigates both issues.
[2]: But a proper UL-listed plug-in solar inverter doesn't have either of these problems. Both issues are sidestepped because it outputs nothing when the grid is down, as a baked-in function. So there's no energized male plug to be a hazard, and there's also no interlock required to ensure that the grid isn't backfed while it is down. You can hypothetically unplug the solar inverter from the wall on a bright sunny day and lick the prongs, and nothing happens.
> When we had our solar installed, we had to make sure we had a newer power meter that could handle power both ways, so it probably is a problem for some situations, but the power flow for a single solar panel into a plug isn't enough to trip this, or maybe newer power meters are better?
This has very little to do with the power meter itself, and more that the power company wants to be able to monitor if the meter is 'running backwards' (i.e., if power is flowing out rather than into the meter). Older meters could only run in one direction.
> Clearly some people think of it differently if they're plugging generators into wall sockets to power the whole house, dumb as that may be.
There's frankly nothing wrong with this if you do it properly. The 'proper' way would be to have a generator input socket near the main breaker panel, and the main breaker is interlocked with the generator input (i.e., only one can be on at a time). You absolutely can just plug a regular generator into a wall, assuming you aren't overloading the wiring or breakers... the safety issue is overblown. The reason why it's 'super dangerous and bad stuff will happen' is because people are stupid and forget to turn off the main breaker. Which, admittedly, is a reasonable concern because... people do forget.
Electrically, this is no different to a regular rooftop solar system. All inverters connect to your household wires like any other device, except that it’s normally on its own circuit and breaker.
What’s the issue? Electrons flow both ways… Just have to synchronise the AC signals of the inverter to the grid, have good limits on frequency and voltage fluctuation, and monitor for faults properly.
This is also how generators work, so it's not new at all, though with a generator you need to disconnect from grid power so you don't electrocute lineworkers. The solar backfeed devices don't work when the power goes out to avoid this (called anti-islanding).
Is it not almost similar to IPS? the device is charging through the power outlet, whenever the power is out, it's inverting and feeding power to the home. This exists for over 20+ years iirc? It works, and haven't heard of any incidents.
EEE here. I've not looked at these in detail myself as they are illegal in my country. Off the top of my head, the big problem I see is that, since you are injecting power BEHIND the circuit breaker an end-user can overload a circuit.
i.e You have a circuit with max current 16A; clever end-user plugs in 3 x 800W panels into different sockets BUT they are unfortunately on the same circuit; now 26A can be potentially drawn through a single cable IN THE WALL. The cable is not rated for that. This is a BIG fire hazard.
And you can't wave this away with instructions. It has to be 100% impossible for an end-user to do this.
Wouldn't all three being plugged in be likely to trip the breaker, because it's just AC and the breaker can't really tell whether energy is flowing "forwards" or "backwards"?
Seems like the worst case scenario is when you mix solar panels with load on the same circuit.
800W at 110v is about 7 amps. Suppose you have a 7 amp solar inverter plugged in as the first thing on that circuit. Further down the line, you have 22 amps worth of load. The circuit breaker sees 15 amps, but the wiring between the panel and the load is carrying 22 amps, which would ordinarily trip the breaker but it doesn't because the solar setup is masking it.
I'm not an electrician. Perhaps wiring code has enough safety margin that being 800 watts over on some circuit isn't actually a serious safety concern, but I could understand why this might not be allowed.
The EU is on 230v, so maybe it's a bit more practical over there because you can add twice the solar capacity for the same amount of additional current you'd have in the US, so they aren't eating into the safety margin quite as much. Though it seems they also use thinner wire gauge generally, so maybe the difference is moot.
Yup. Worst case scenario is indeed mixing generation and load on the same circuit. And you have to assume that some number of people will manage to do that and create a fire hazard. To connect it safely, you need to know the circuit layouts and the rating of the cables. This is not something solvable with a safety sticker and safety instructions. A huge amount of effort has gone into making domestic electrical installs as inherently safe as possible and these panels are a back door to that.
Don't get me wrong, I think they're a spectacular idea, especially for renters. But you'd need an electrician to check the circuit and maybe even have a special balcony-solar-plug to prevent people plugging in too many panels in the wrong locations.
Quick edit: Random idea. I guess if the panel could communicate with the RCBO it's connected to and that RCBO can dynamically alter it's trip current could also solve it. But again, that's an electrician call and new thing installed.
That's why in Germany you are limited to at most 800 W for you house with plug-in solar.
Of course your argument still stands, but we're talking about at most 3.5 A extra current, not 10 A. Home installations seem to be adequately sized to be able to handle that load. At least I'm not aware of any reported incidents, and people have been putting them up for quite a few years already. And typically, German regulations err on the side of caution.
But sure, with 110 V, you will have more problems with the extra current for the same power, so in the American grid there could be further precautions necessary.
You cannot rely on that limit though. People WILL plug in more than that. The whole system has to be kept inherently safe. All other concerns are solvable, but I don't see how you solve this, bar having a special balcony-solar-socket installed where an electrician has verified that it will be safe in all scenarios.
Americans are, for the most part, fucking morons. We invented the infamous warning labels like DO NOT EAT THE TONER CARTRIDGE or DO NOT HOLD THE CHAINSAW BY THE BLADE or REMOVE CHILD BEFORE FOLDING STROLLER or PEANUTS: CONTAINS NUTS
We're also very litigious, as it isn't hard to convince a jury to award damages to a fellow moron.
Everybody in the world is a moron. Americans just recognize some places where we are morons and try to prevent stupid people (which includes me and you!) from doing some stupid things.
Not everything, Americans do get by with doing other moronic things that other countries do things to prevent. However other countries also do their own moronic things that Americans are much less likely to.
Italy has the "Do not store your cat under the seat" warning. They do NOT put it on Italian-market scooters and they definitely DO put them on US-market scooters.
It would in practice be (mostly) fine, just as it is elsewhere. But electrical safety principles in the US are typically "must be safe regardless of the dumbest possible use" so that "mostly" is a big obstacle.
I would contest it's without incident. The US is higher risk since it uses 120V => the currents are x2 higher and US electrical safety standards are an eclectic mess of: world leading and 3rd world.
I sincerely get your concern. Clearly explain on the box what NOT to do and be explicit about the risk. Use an icon of a house on fire. Done. Life is risk, and regulating and banning things based on the lowest common denominator of human judgement is a fool's errand. Should we ban vehicles as well since about 40k people die from vehicle related fatalities annually?
In my view it's more that: electrical safety has advanced to it's current "version" and allowing these panels is a regression in safety. There's already plenty of products/theoretical-products that are banned and/or tightly controlled for electrical safety sakes (suicide cable is the poster child).
To use your car analogy, we're not banning vehicles. We're disable one of the airbags when enabling fuel economy mode.
I’d also guess bad inverter hardware could cause lots of dirty/noisy AC power effects and damage other equipment on the system. This definitely doesn’t sound like a very safe approach without a lot of conditions being met and exactly like your example there are too many ways it can go wrong.
Wait, people in the UK actually follow those instructions?
In the US, even with a warning, you'd get regular home fires as people hooked one of these panels into every available outlet just because they can. I wish I were joking.
I hope it's at least "probably fine". I've seen some pretty shoddy electrical work in my lifetime (including new installs) and am now of the mind that the deep-defense-in-depth of electrical safety we have these days is to also "cope" with shitty electrician work.
There is a YouTube video where a guy tested how many amps are required before a fire starts and it was like 70 iirc. 30 amps didn’t even get the wires hot. I’m not sure that’s true after several hours of continuous usage of multiple space heaters plus plug in solar, for example. It’s not a risk I would even entertain but I think the real risk is pretty low.
I have two sets of these..very cheap if you order it on Amazon yourself. And very easy to connect.
The big panels are a bit of a hassle because of the size, not the weight.
So your home has multiple circuits. Each outlet in the home is on one of these circuits. If you want to power your fridge, I assume the panel needs to be plugged into the same circuit as the fridge. Is this correct that “you are powering a circuit, not your house”?
No, I think the idea is it backfeeds into everything connected by the same wire -- unless the grid shuts down entirely and there's no 60-cycle signal to synchronize to, in which case it shuts down for safety.
No this is not how circuits work in your house. While they are each protected by a separate breaker they are all sharing the same power from the panel bus.
The breakers do not prevent power flowing from an outlet back into the panel bus.
> concerns that the energy being pumped into wall sockets could cause wiring in old homes to catch fire, but he says “that’s never happened in Europe,” despite its widespread adoption.
well old NA circuits are notoriously shittier and lower-amp-rated than in europe lol
i don't think it's a good argument against balcony solar but neither is that a good rebuttal
NA is typically higher amp rated than europe. Europe has a lot of 10 amp circuits, 15 is the smallest you will see in NA (you can have smaller in special circumstances but I've never seen it). You might be confused because the US often uses 120 volt circuits which means 15 amps is less watts then 10 amps 240 like you see Europe.
Don't call the US system "shittier". It is different, but that doesn't mean better or worse. Anytime the US needs more a little more power we put in 20 amp circuits for the same wattage. Anytime we need a lot more power we put in 240 volt circuits. Different, but it works just fine.
I did the math for my rates and missed opportunity costs and the payback is almost 8 years for 900w system at $1500 which is cheap. Do your own math before you purchase
Once this becomes cheap enough and easy enough, I expect heavy handed regulation pushed by the power companies. Chances are we will buy these, plug it in and our energy bills will be the same or more!
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[ 0.26 ms ] story [ 13.1 ms ] threadI am thinking along the line of:
The more stable you think the future will be, the more you want to capture the efficiency of central power.
In other words, it can be useful even if it's not the most efficient way to do it. It only has to be more efficient than the status quo.
I don't have thd capital to build utility-scale solar. I do have the capital to install residential solar. My electricity is now cheaper.
Utility companies are not incentivized to lower prices because it means less money for them. Do you remember when power companies told people to conserve power and then people successfully did this? And then they raised rates because they weren't making enough money? This happens in California ALL THE TIME. I've lived here 30 years in Silicon Valley and it's the biggest scam that no one talks about. It happens with electricity and water. With water its even more egregious because they told us to conserve water because of the "drought" but once the drought was over, they raised rates because people weren't using enough water. My connection fee to water is over $100/month without spending a drop of water. That's why I stopped conserving water and water my lawn every single day because it turns out that my water costs are only about 1/3 of the actual water bill costs so fuck it!
It's the same playbook over and over again, there's no incentive to lower rates at all because it's an easy way to make money over an entire population of tens of millions of people.
Now PG&E is fighting to charge solar panel owners $100+/month just for the privilege of being connected to the grid. That would make having solar panels even more expensive than not having solar panels which is utter hypocrisy but no one seems to care or point this out. It's a complete and utter scam.
The day after the system goes live, they'll probably announce flat rates for any time of day, just to f' with me. :(
I am a staunch DIY serial entrepreneur techie that has used my grey goo to build and sell a few companies and my time now is spent similar to yours although using a different application of physics. I too am motivated, just as you are, in my efforts to apply what I know to further reduce my energy costs which will not stop rising for quite some time.
You really made my day with this post and I hope we can find more folks like ourselves from your share because in time 'dogfooding' new ideas at home will lead to new applicable discoveries for all.
Stay Healthy!
https://www.youtube.com/watch?v=IA15VkLlx-w
Its like a large freezer gel pack.
Enjoy.
Every system like yours works to flatten the prices, but it looks like a pretty big swing between peak and off peak pricing today, so it'll probably be a while before flat pricing again.
For example Duke is for profit here in Florida, and charges about 25% more per KWH than OUC that is a public utility.
This leads to pricing where on one street your power bill is $250, but one street over its $200, often coming from the exact same power plant.
FPL is also for profit, and is cheaper than OUC.
1st 1000kwh with FPL are $0.11461/kwh Above that is $0.13461/kwh with a base customer charge of $10.52
1st 1000kwh with OUC are $0.1155/kwh Above that is $0.1405 with a base customer charge of $18.50/mo
Total cost with FPL for 1000kwh for the month before state and local tax is $125.13
With OUC it would be $134.
https://www.ouc.com/wp-content/uploads/2025/09/2025_10-OUC-E...
https://www.fpl.com/content/dam/fplgp/us/en/rates/pdf/reside...
The biggest factor Id say is FPL has significant amounts of solar and nuclear generation.
https://www.fpl.com/content/dam/fplgp/us/en/news/2025/fpl-ne...
18.8% Nuclear and 8.4% solar (more than double the national average!)
OUC on the other hand has less than 3% Nuclear (generated / purchased from FPLs plant on Hutchinson Islans!) and <6% solar, with a massive 24% still being generated by coal! (FPL demolished their last coal plant ~8 years ago in Indiantown, I watched it live!)
https://www.floridapsc.com/pscfiles/website-files/PDF/Utilit...
So while FPL is technically for profit and OUC is not... FPL is cheaper and greener than OUC.
I say this as a long time Florida resident who remembers when FPL truly sucked in many ways. They’ve, demonstrably, put in effort to make electricity greener and cheaper here in FL. (Even with all of their efforts against home solar).
And since transmission cost is typically bundled with the energy cost, it means the final retail energy price has to go up to cover the transmission cost.
Why? Overall transmission cost are defined by highest possible consumption, and solar panels have practically no effect on that parameter.
Just how many natural disasters do Americans go through before realizing that?!
These disasters are rare though for any one person - a few happen every year, but it will be years between you personally seeing a disaster. That is why generators sell out when there is a storm: even if you have a generator odds are it is rusted and won't work. It is a waste of money to buy a generator before you need it.
This is one of the most condescendingly-wrong posts I've ever seen on this site and you should be embarassed for writing it. The beginning was just typical hn hubris that I probably wouldn't have responded to, but that last jab at the end in the context of an active and ongoing emergency that you clearly know nothing about is completely insensitive and gross.
Having traveled to those areas many times to assist with recovery, slept in trucks for weeks, and made many friends in those areas: It's day four without power and that is not abnormal. Bigger storms you can go weeks without power. Batteries aren't gonna cut it.
And gas generators have a whole mess of problems.
- Gas doesn't store well. Your stored gas is gonna go bad. That means when you find out a hurricane is coming to your area you can spend your time either protecting your house or wait 3-6 hours in line to hopefully get some gas for your generator before it runs out. Maybe they are rationing to 5-10 gallons.
- They might not work after sitting for years, even when properly maintained (one of my friends had two and neither could get running even with help). Hurricane areas are humid: generators rust. If you don't use gas engines the seals dryrot. If you leave them sitting with gas in them the ethanol (sugar!) Separates out and gums it up, breaking your generator. If you stop using your generator in the wrong way then you'll break it (you need to run it dry, using/wasting all the gas in the tank).
Even if you score gas and your generator works that brings us to the next problem:
The gas stations can't pump gas if they have no power themselves. They also can't be refilled if the big gas tankers can't reach them due to trees blocking roads. Main roads become passable quickly, side roads might not work for weeks. Cell phones might be out for weeks (and modern 5g micro-sites will take even longer to get fully rebuilt across a whole county). If your close-by station can't get gas you can't just call around to fine somewhere that does. You can't just drive around either. Single lane roads mean going anywhere takes forever and you are actively hindering recovery efforts. There are still stations in florida unable to pump gas due to shortages or power loss. So your couple of gas cans got you through a couple of days, what now?
And gas generators have moving parts. They are complicated. Another friend there had theirs die the day after the hurricane. Shit happens.
There is a reason prevalence of gas geberators in hurricane areas is less than 5% (I probably hear one running for every 50 houses, but most run them only intermittently) and it isn't because they're just dumb hicks who aren't as smart as mschuster91.
Lastly, you need to know how to use one. Every time there's a hurricane someone puts it in their garage and poisons themself and their family to death. Should you know better? Yes. But everyone doesnt.
Then there's all the other ways you suddenly need to spend energy to survive: you need to boil water, sometimes for weeks (while you don't have power), you need gas for your chainsaw to clear roads/trees so that power and water can be brought back. You need to drive to get supplies. Wasting gas that could be used to recover from the disaster isn't wise.
Back on topic: A stack of solar panels that could plug into the same outlet as a fridge would be a godsend for a lot of people (while also storing better than a generator and being more compact -- so more can be trucked in after a disaster.)
This is a nice grassroots technology that lets motivated individuals take action.
There is also the problem of backfeeding, but this is more theoretical - even if you know to limit your power use, your neighbors won't and so your generator will trip its own breaker. Linemen are taught to either treat power lines like they are live, or to short them to ground - it can happen they don't do this and you kill a linemen, but still not as big a worry as it is made out.
They make generator "inlets" that sidestep all these problems when used correctly. Most common I've seen is a block so you can't have the inlet and the main breaker both on at once.
it is not theoretical from the POV of power company employees working on their lines. the power goes out, they go to fix the equipment or wiring, and if the inverters connected to the grid have not shutdown, there could be 10s of kW to even MWs being backfed into the system they are working on.
that's why in the US at least, grid-tied inverters are required to have protection against this. if they do not see power from the grid, they shutdown (and rather quickly).
I realize this is a complete noob question but I'm still curious: with enough "backfeeders" could it not in theory be possible that the backeeders see each other's output and keep operating?
Say, a few houses at the end of the line, each with very little electricity consumption (no-one's at home), but with panels and inverters going full tilt, something like that?
(the specific case of very little consumption but panels and inverters going full tilt doesn't work as this would lead to the frequency rapidly increasing, exceeding inverter set points and the local grid collapsing with all the inverter tripping off. The danger scenario is closely matched load and generation, like a real grid)
Perhaps a more robust solution would be for the power company to install remote-switchable circuit breakers at various places of the grid. Use some sort of wireless IoT protocol to listen for "on/off" signals and to report back "I'm now on / I'm now off!". Then the power company can disconnect parts of the network by themselves, without trusting that every inverter, generator and battery will do the right thing.
Also, people have been back peeking the grid from their home generators for decades by now. Solar and inverters are a different variation of that attack, but it is nothing new. Any utility will have procedures because they can't guarantee that's not happening and we learned years ago.
I'm not saying it never happens, only that correct procedure already makes it not an issue
tl;dr Plug-in solar inverters must power off within a second if they stop detecting the grid's sine wave.
Generators have no such protection and will happily backfeed through the transformer outside your house to energize power lines. Line workers are careful, but there have been deaths. After hurricanes seems the most common based on a quick search.
So it's not a stupid question, indeed you should never plug a generator into an outlet. The double-ended "suicide cord" which allows you to do that has that name for a reason. (It can be fine to plug a generator into an inlet circuit, if the electrical panel has a proper interlock that physically forces disconnect from the utility before connecting the generator inlet.)
The better way (and legal way) to do this is to have a generator plug plug installed, this way when you switch over to generator your property is disconnected from the grid.
It can be quite safe to plug a generator into an outlet if you take precautions to properly island the system. I had an interlock on my breaker panel that would let me turn on a 50A backfeed breaker if my main breaker was switched off.
Solar inverters (esp for this use, but also in general) are grid following; they'll use the existing frequency and support it, and if the grid goes off they'll go off too and do no power-off backfeeding.
The inverters are thus broadly safer to be plugged in to systems that are otherwise unprepared.
Generators could be made grid-following (many are now inverter-based), but for most users that would be silly, since the supplemental power would be more expensive (and louder!) than from the grid.
Most modern meters will debit and credit the electricity going in and out on both split phase lines as net meter, so the electricity consumed in the other split phase is counted as consuming the plug-in power. However some old meters add the outgoing electricity up as consumption so you are paying for the electricity fed into the grid. Call your utility company to make sure.
Also, unless you have a net metering agreement with your utility company, you won’t get paid for any excessive electricity fed back into the grid.
Plug-in solar is suboptimal in many ways, but it does sidestep a lot of those hurdles. Not too surprised to see it on the rise.
Another thing that might be worth keeping in mind is that plug-in solar panels are often installed vertically - i.e. balcony solar. In which case the peak of the panel's generation is offset to the edge of the typical "duck curve". If it gets popular enough to affect the grid, it might get the solar-induced demand slump larger, but make the edges even sharper.
Would that make grid scale battery storage with its instant response even more important?
The plug in solar systems are small and usually mounted in ways that don’t capture as much energy as the same panels mounted on a roof. These systems aren’t going to get popular enough to make a big difference in anything.
I think it’s nice that they’re available for people to do some small scale offsets, but I think they’re more of a gateway to better solar installations. They also send people down the path of investigating battery storage add-ons, which might actually be a better long term solution for everyone.
If we can get to a point where we can buy plug-in batteries that are subsidized by requiring coordination with the grid, the power companies could get distributed, controlled battery storage to work with their demand curves. This can already happen with the bigger permanent install batteries.
They already are in a few countries.
Also, with the price of solar panels decreasing below most (wood?) building materials with way higher durability, no paint required, why wouldn't it replace most sun facing siding applications aside from being "ugly".
Obviously the inverters and pairing technology exist, but I don't know where to buy one retail.
welcome to the future
https://shop.sveasolar.de/category/ikea-shop
One constraint on these I've read is that if you have sources and sinks on the same circuit, you might overload the line without tripping the breaker at the box. If I'm understanding this correctly this has caused them to limit the power of plug-in solar to a fraction of what a single circuit could potentially carry.
My electricity supplier sends me a message nearly every week saying if I use less electricity during peak demand times then I get free power at weekends. https://octopus.energy/saving-sessions/
While the power doesn't go out often, it is a big deal when it happens and so a backup is useful. I'm still fixing the damage from the last one - the sump pumps not running for an hour in a rain storm is expensive. Fortunately it wasn't a long outage, much longer and the fridge/freezer would be a problem. In cold weather the furnace is important to keep running. There are other essential things as well that my house cannot survive without. Beyond that I want my computers to keep running if possible.
My sump pump hadn't run at all to my knowledge (I hear it so I think I'd know but maybe I was always gone or sleeping) for several years, but the power went out in a big rain storm and so the one time I needed it, it didn't run. (my old generator didn't kick on like it is supposed to, but I'm not sure if that circuit is wired to the generator anyway)
With fixed solar installs you're likely to find some kind of switch or labeled breaker to disconnect. The system is designed with a central "power in" that's (hopefully) obvious when you're standing in the breaker room.
These things could be injecting power anywhere, so you need to know they're there (which may be less apparent than roof/field panels) and go around and pull the plug(s). Relevant to electricians, firefighters, etc.
They’d also probably depend on a power signal to frequency match.
Your circuit breaker protects your circuits by putting all the load (eg your microwave) on one side, and your supply (mains power) on the other. If too much load is present, the circuit breaker trips.
However, plugin solar puts invisible supply on the load side, which your circuit breaker cannot see. Let's make an absurd example so you can see what the problem is, then scale it back.
Imagine someone buys 5 panels that can each supply 5amps. They plug them into outlets on a 40 amp circuit. They then proceed to run their toaster, microwave, vacuum, and hair dryer. They can draw 65 amps through the wires before the circuit breaker trips. (40 from mains, 25 from the panels)
Let's say they had a good electrician who installed 6AWG wiring on that circuit, which is rated for 50 amps. The circuit breaker used to trip at 40, so no problem. But now up to 65 can go across the wires and suddenly you are exceeding rating for wires.
Now you might say, "most of these are 3.5 watts, and they clearly say don't use more than one". But I say that's a "good intentions solution". We should make it mechanically impossible to do the wrong thing. Maybe these panels could try to communicate over the electrical wires, and if they detect a signal from another panel they should self limit. Maybe we need to rethink circuit panel design. But as it stands people will absolutely buy one of these, decide they love it, and then buy 4 more.
In the original example, RCD/circuit protection is regulated on the _property_ side, e.g UK has EICR for electrical install. Once its done for a property, its good until next inspection (in theory)
This moves the protection to the _appliance_ , which while it needs to meet certification, is much harder to police a consumer electronic device, than a physical unmovable premise.
I think these are great, but there will inevitably be devices that don't implement the spec correctly that still get sold to willful or unwillful consumers that result in danger to everyone.
I think this is probably fine, since UK circuits are typically 20A. Apart from fault current (which would have to be line to line, since line to ground would trip the RCD), it's quite hard to end up with more than 20A of stuff plugged into regular sockets unless you're overinvested in portable heaters. All the big stuff - cookers, heat pumps, showers - is on separate breakers from the sockets.
Circuit breakers trip bidirectionally, so the circuit breaker itself would protect if too much current is drawn through to the mains panel.
How, precisely, would you get 65A through the wiring on this 40A circuit, if I drew 40A of consumption and had 25A of supply?
The 25A cancels out the 40A, so the upstream feed would only see 15A total. You do get 65A of total current drawn through the breaker panel, which is a concern, but the supply wiring would not see 65A. Subpanels (which, this would be a subpanel if it only had 40A capacity) are typically going to be just fine.
In the UK you typically make a ring circuit. In the US you make branching circuits.
In the US you get: Mains -> Breaker -> Outlet 1 -> Outlet 2 -> Outlet 3.
In the UK you get: Mains -> Breaker -> all outlets -> Breaker
In the US, assume I had 65A of load on outlet 3 -- I've plugged in too many things into a surge protector. Assume a bunch of solar panels are on outlet 1.
The the diagram looks like: Mains -40A-> Breaker -40A-> Outlet 1 -65A-> Outlet 2 -65A-> Outlet 3
Now, the breaker won't trip because only 40A are crossing the breaker. But 65A are on the wire between outlet 1 and 2 and between 2 and 3.
Decentral battery units in substations, similar to what Tesla did in Australia many years ago. They can absorb or provide reactive power as well.
I think this will be your biggest practical issue in newer US construction. Arc fault circuit interrupters are now code for any wiring in living spaces. They can be quite sensitive to weird switching loads (and sources). I was forced to swap an AFCI for a normal breaker in my last home. The power supply in my workstation triggered the detection heuristic in the AFCI about once a day. I could cause an outage on demand by running certain workloads.
If you want to get an overview of the ecosystem, googling "Balkonkraftwerk" gives you the most relevant results.
I passed high school physics with good grades, so … I’m not surprised other people instinctively say this can’t possibly be a good idea.
What's new is cheap and ubiquitous micro-inverters. Before it wasn't worth putting a $800 inverter on a small 2-panel 600 or 800 installation. Now with micro inverters being so cheap, this tech becomes viable. And with loads so limited (less than a microwave) the regulation is equally light to allow this convenient plug-in solution.
But it’s AC, the electrons are shuffling in both directions at 50/60hz
Voltage goes forwards and backwards and odd but current also goes forwards and backwards, for both appliances and generators.
The difference between consumer and producer is only the phase angle between the voltage and current waveform.
Because power is VxA, do that across the wave cycle and the power direction changes for consumers and producers.
At every junction, Kirchhoff’s current law will sum the currents so you get a “net current” waveform on a wire that might have both a kettle and a plug in solar panel.
That summation means the kettle will chomp as much current as the panel can deliver and than take more from the grid. Swap the kettle for a small LED which takes a fraction of the current and the sum gives a NET supply, and on to the next junction.
It took me a while to get my head round it too.
Take power out of the flywheel? Sure, why not -- that's exactly what we've done with it at home since we had an AC grid to speak of.
Try to impart higher voltage to put power back into the system? Fine, no worries. Flywheel just accepts and absorbs whatever you put into it as long as it fits.
Try to change the flywheel's AC frequency or waveform, though? Hah, fat chance: Flywheel will trip your breakers or reduce your gear to ash -- whichever comes first. We play by the flywheel's rules, and those rules aren't optional at all. It may be just a big dumb flywheel, but the flywheel's enforcement is absolute.
Anyway, it's a big mythical flywheel. We get charged money to take power out of it, and (with the right arrangements) we get paid money to put power into it.
And by design, grid-tied inverters are quite good at following the flywheel's rules. They match the flywheel's waveform very well [lest they go poof]. They can only put power into that flywheel, and they reject power from that flywheel. The inverter is a one-way thing that, from a high-enough viewpoint, looks kind of like a check valve or a diode does.
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But it's not an ideal, perfect system. It does not exist in a world of frictionless pulleys and ropes that don't stretch.
That imperfection shows up in the wires and transformers connecting the house to that flywheel system, in that these parts have a non-zero impedance. (For the sake of this discussion, impedance can mean about the same thing as resistance)
And that impedance is useful. It means that we can increase voltage a very tiny bit on our local leg, and thereby succeed at using our puny little solar power system to help cover our own local base load.
Suppose our plug-in solar widget can produce 800 Watts today. The plug-in kit increases the voltage that it drives that plug with until 800 Watts of power output is achieved (which is only a very tiny amount of extra voltage, but it's real anyway). This is its purpose: Where some robots pass butter, this robot puts 800 Watts into a power socket.
Since the wiring between the plug-in solar and the local household baseload stuff has a lower impedance than the mythical flywheel does, our baseload stuff (the fridge, the router, the fan by the window) gets first dibs at that 800 Watts of minutely-enhanced voltage.
If we produce more than we use, the excess local power production gets provided to and soaked up by the flywheel (maybe we get paid for that).
If we use more than we produce, then the deficit is made up for by the flywheel (and we definitely pay for it).
If our generation and consumption is perfectly balanced (which never really happens), then the flywheel plays no real part in the program except to provide a waveform for our solar inverter to synchronize with.
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Anyway, it's not new tech at all. It's safe in that it won't work at all without a connection to the big flywheel in the sky. And folks have been using grid-tied inverters for quite a long time, but that was done on a dedicated circuit (with a dedicated breaker or fuse or RCBO or whatever they're called wherever you are).
An important new part is that it can be a plug-in system that works without individual planning or permitting: A person can legally buy and use a kit without obtaining extra permission.
Another important thing is the safety of sharing a circuit since enhanced potential exists for overheating things. Germany limits their plug-in solar to 800 Watts, or about 3.5A @ 230V, while their circuits are usually 16A.
That means there could be as much as 19.5A of nominal current flow within a circuit be...
Current load pulls the voltage down, sourcing current pushes it up. No bother, as long as your sources cut out if the voltage goes too high, and your loads cut out if it goes too low.
In terms of electricity and physics, this is unremarkable, the bit that probably scares people is the fact that you have a plug connected to something that's _outputting_ AC, particularly for those of us with 240V supplies.
If it were any old AC source on the other end they'd be correct, but current technology allows the output to be cut in milliseconds, faster than the period of a single AC wave, once the plug is removed.
Tangentially; if you have solar (mine's roof-mounted) don't assume that flipping the breaker means there's no power; I live in a 1930s UK home with all sorts of interesting wiring and flipped the breaker to change a plug socket, only to be shocked; literally and figuratively when it was hot.
When we had our solar installed, we had to make sure we had a newer power meter that could handle power both ways, so it probably is a problem for some situations, but the power flow for a single solar panel into a plug isn't enough to trip this, or maybe newer power meters are better?
We definitely think of it as somewhere a power comes out of, but I don't think it's the name, just that it's only ever been that way.
Clearly some people think of it differently if they're plugging generators into wall sockets to power the whole house, dumb as that may be.
My home is 1930s, it's fuse, in the black Bakelite housing typical of the era was insufficient and we were missing a incoming breaker to/from grid, those were updated. Our meter is much more recent, though still dated; allegedly it would have worked but it wasn't a smart meter, which we wanted so we had that updated.
I've also heard through my many hours of watching Solar videos on YT before our install that some breakers, RCDs(?), RCBOs(?), whichever it is, aren't always suitable for bidirectional current flow, so that's a possible issue too.
All of that is aside the "suicide cord" danger of the old generator method, but that's gone now with modern tech, the output is cut before you can get your hands on the contacts on the end of a plug.
It's just been legalised here in the UK, and I think it will help people with their bills, but the key is to keep installation costs down; if it's DIY you can look at a decent ROI time, but with the cost of trades-people these days, if you have to call out a sparky to inspect before you plug it in, you've added potentially years to your payback period.
At ~800W, I think on the whole we'll be fine; the equipment in our homes has got much more efficient over the years, and our homes were mostly built for times where we were using higher powered devices. If you can draw over a kW to power an electric heater or kettle, I don't see why feeding a mere 800W back in would be a huge risk.
Disclaimer: I'm not an Electrician, but I do have a degree in Electronic Engineering.
The solar is the same way, but with an auto cutoff.
Yes, but that's dangerous for reasons[1] that people often don't bother explaining -- and that aren't important for solar grid-tied inverters[2].
[1]: The seemingly-ideal way to plug a big fat generator into an American house in a hurry is to use a double-ended suicide cord to feed into the 240v dryer outlet. That provides plenty of power to get a lot of things done things, it's a single-outlet circuit, and it lights up both sides of the split phase panel. But that's bad.
The most obvious way that it's bad is because we shouldn't have energized male prongs. Like, ever -- that's just extra shit to get hurt with. But this suicide cord idea relies upon their use.
The other way that it's bad is that the generator doesn't know whether the house is still connected to the grid or not. So unless we deliberately disconnect from the grid, there's a wonderful chance that we feed it even though that grid is presently non-functional. This can fuck people up: The transformer on the pole outside (or in the box down the way, or whatever) will cheerfully convert the sleepy 240v from the generator into thousands of volts on the wires outside that were completely dead until someone decided to get clever. Now, the guy cleaning up storm debris down the block or the lineman doing the repair gets the fuck shocked out of them in spooky-dead kinds of ways. (Yeah, yeah: We shouldn't ever do anything near downed lines of any kind, and the lineman should always have appropriate PPE. And we shouldn't plug our generators into our dryer socket, too. Death is permanent.)
Panels with interlocks and wall-mounted male sockets exist that can accept generator input both exist, and the combination of them mitigates both issues.
[2]: But a proper UL-listed plug-in solar inverter doesn't have either of these problems. Both issues are sidestepped because it outputs nothing when the grid is down, as a baked-in function. So there's no energized male plug to be a hazard, and there's also no interlock required to ensure that the grid isn't backfed while it is down. You can hypothetically unplug the solar inverter from the wall on a bright sunny day and lick the prongs, and nothing happens.
This has very little to do with the power meter itself, and more that the power company wants to be able to monitor if the meter is 'running backwards' (i.e., if power is flowing out rather than into the meter). Older meters could only run in one direction.
> Clearly some people think of it differently if they're plugging generators into wall sockets to power the whole house, dumb as that may be.
There's frankly nothing wrong with this if you do it properly. The 'proper' way would be to have a generator input socket near the main breaker panel, and the main breaker is interlocked with the generator input (i.e., only one can be on at a time). You absolutely can just plug a regular generator into a wall, assuming you aren't overloading the wiring or breakers... the safety issue is overblown. The reason why it's 'super dangerous and bad stuff will happen' is because people are stupid and forget to turn off the main breaker. Which, admittedly, is a reasonable concern because... people do forget.
On an AC circuit, all connections are duplex.
It needs to be paired with a transfer switch or it will backfeed.
Unfortunately it is a far too common thing for people to rig these things up themselves leading to all sorts of funny complications.
i.e You have a circuit with max current 16A; clever end-user plugs in 3 x 800W panels into different sockets BUT they are unfortunately on the same circuit; now 26A can be potentially drawn through a single cable IN THE WALL. The cable is not rated for that. This is a BIG fire hazard.
And you can't wave this away with instructions. It has to be 100% impossible for an end-user to do this.
Seems like the worst case scenario is when you mix solar panels with load on the same circuit.
800W at 110v is about 7 amps. Suppose you have a 7 amp solar inverter plugged in as the first thing on that circuit. Further down the line, you have 22 amps worth of load. The circuit breaker sees 15 amps, but the wiring between the panel and the load is carrying 22 amps, which would ordinarily trip the breaker but it doesn't because the solar setup is masking it.
I'm not an electrician. Perhaps wiring code has enough safety margin that being 800 watts over on some circuit isn't actually a serious safety concern, but I could understand why this might not be allowed.
The EU is on 230v, so maybe it's a bit more practical over there because you can add twice the solar capacity for the same amount of additional current you'd have in the US, so they aren't eating into the safety margin quite as much. Though it seems they also use thinner wire gauge generally, so maybe the difference is moot.
Don't get me wrong, I think they're a spectacular idea, especially for renters. But you'd need an electrician to check the circuit and maybe even have a special balcony-solar-plug to prevent people plugging in too many panels in the wrong locations.
Quick edit: Random idea. I guess if the panel could communicate with the RCBO it's connected to and that RCBO can dynamically alter it's trip current could also solve it. But again, that's an electrician call and new thing installed.
Of course your argument still stands, but we're talking about at most 3.5 A extra current, not 10 A. Home installations seem to be adequately sized to be able to handle that load. At least I'm not aware of any reported incidents, and people have been putting them up for quite a few years already. And typically, German regulations err on the side of caution.
But sure, with 110 V, you will have more problems with the extra current for the same power, so in the American grid there could be further precautions necessary.
We're also very litigious, as it isn't hard to convince a jury to award damages to a fellow moron.
Not everything, Americans do get by with doing other moronic things that other countries do things to prevent. However other countries also do their own moronic things that Americans are much less likely to.
https://members.modernvespa.net/brian_herwick_-_coolass/uplo...
To use your car analogy, we're not banning vehicles. We're disable one of the airbags when enabling fuel economy mode.
> you can't wave this away with instructions
But apparently you can with legislation about instructions.
Edit: government safety investigation https://assets.publishing.service.gov.uk/media/6a32bfea0bea2...
In the US, even with a warning, you'd get regular home fires as people hooked one of these panels into every available outlet just because they can. I wish I were joking.
I hope it's at least "probably fine". I've seen some pretty shoddy electrical work in my lifetime (including new installs) and am now of the mind that the deep-defense-in-depth of electrical safety we have these days is to also "cope" with shitty electrician work.
And it's the way it should always have been.
Sure, there are concerns with possibly melting house wiring, but they require some vanishingly unlikely situations to occur.
The breakers do not prevent power flowing from an outlet back into the panel bus.
well old NA circuits are notoriously shittier and lower-amp-rated than in europe lol
i don't think it's a good argument against balcony solar but neither is that a good rebuttal
Don't call the US system "shittier". It is different, but that doesn't mean better or worse. Anytime the US needs more a little more power we put in 20 amp circuits for the same wattage. Anytime we need a lot more power we put in 240 volt circuits. Different, but it works just fine.
https://octopus.energy/plug-in-solar/