I think this is something that may happen in the next decade.
The interesting impact will be on the grid itself. Why connect to the grid if you are self-sufficient?
Then the grid starts to degrade due to lack of maintenance, and the people that can't afford local storage become dependent essentially on a government maintained service.
Or should we be planning localized storage and grids at the same time, so we get the benefits of both scale and resiliency and redundancy.
People will be parking a mobile 100kWh battery at their house every night. We need integrated V2G and grid upgrades to make the most of this opportunity.
> Why connect to the grid if you are self-sufficient?
I grew up in Australia used to a grid averaging perhaps an hour’s downtime in the typical year. But now I live in India, and not only is the power frequently off for hours at a time (it’s a rare week that lacks an hour of downtime, and five or ten hours isn’t uncommon), the quality of the power is also far lower, and it damages hardware. It’s normal for AC units to need mildly expensive component replacements every year or two due to electrical damage, even with the obligatory voltage regulator in place, whereas in Australia I think most people never need to professionally service their AC until it completely packs up after maybe 15 years. If you’re going to want a decent-sized inverter and batteries anyway to get reliable power, then so long as you can get enough solar panellage, getting those solar panels and more batteries and going off-grid becomes mighty attractive—I suspect a payoff period of under a decade, even with comparatively cheap grid power, partly on the strength of electronics living longer.
—⁂—
Somewhere along the way, it actually becomes mandatory to be connected to such services. In Australia I lived in a rural town of under 100 people, and I asked if I could disconnect from the town water supply, and was told no. So that was some sum of mandatory daily connection fee for something that I would have preferred to unsubscribe from. (Town water was only hooked up to some outdoor taps, and the toilet; the supply had only become treated/potable five years prior, so every house was still hooked up to their rainwater tanks. In fact, the guy I bought the place from said that twenty years earlier you didn’t use the town water on your garden because it would kill the plants.)
That is a trick question designed to make people argue and feel like there is some science or math to it. There is not. Nobody here can accurately predict weather far out enough to be a factor in this decision. The truth will vary by demand by family which may have variability throughout the year or decade. Another variable is the number of cloudy days which will vary as climate changes.
The answer is somewhere in the neighborhood of as much as one can safely store and afford accepting that batteries have a short life. Much like wells in cold climates the batteries should be in an underground insulated vault made from higher quality concrete as to keep fire hazards away from the home. That is also where whole-home generators and fuel belong, in their own vault so they can be easily maintained without having to rent an excavator to dig out the tank.
I'm sure it would be much more cost-effective to have community storage, rather than individual storage, and it would balance the load a lot if some users used more power during th day than at night.
In a manner of speaking, the grid is already the storage mechanism. In summer you sell the excess to the grid; in winter you buy it back. Obviously you pay more to buy than you get for selling but that's the premium for using someone else's infrastructure. You'd spend a load more buying a battery the size of a small house.
I always thought about this myself in terms of personal sized long term, high density energy storage. Compressed hydrogen with a fuel cell is the obvious solution. Excess electric is used in a electrolysis cell and a matched compressor fills a bank of storage cylinders. More cylinders = more storage. Though likely very inefficient with a risk of fire or explosion.
Are there any other long term high density electric storage technologies that can fit in someones basement, garage, or even apartment closet?
Why go for a bigger battery when you can just put more panels on the roof to cover those winter days and waste the power the rest of the year?
I suspect the answer is somewhere in the middle - maybe two weeks of storage. Though of course prices change all the time so the correct action will change and you need to rerun the numbers as things degrade to decide your next action.
Depends on the part of the world, but in northern/central europe the production of panels from september/october to march is zero, 0, according to my colleague in his roof and many others have said the same. It is cloudy, it will rain a lot and during winter if there are no clouds then there are only.. a limited number of sunglight possible, and the sun is low, so most of the "power" is already absorbed by the atmosphere
A few commenters have said this, but the author is in the UK, we just don't have the roof space.
My detached house has less space for solar panels than some smaller homes because all faces of the hip roof are triangular; lots of houses nearby that are semi's or terraced actually end up having more roof space because their roof faces are rectangular.
I managed to have 14x 465W panels total added on the east and south faces of my home, but the installer wanted an extra 40% of the total system price to add 5 more panels (and the 15th they couldn't fit on the south face, for 6 total on the west) because they'd have had to erect additional scaffolding and who knows what else. That was an absurd additional cost so we didn't do it, but that additional generation late into the afternoon would have been great for our peak usage at dinner time. My suspicion is they simply didn't want to do it, because the cost just doesn't add up.
On an overcast day at this time of year I can generate nearly enough to power the "baseline" of the house, but currently I receive 24p/kWh to sell the energy back, and I can charge the batteries at 15p/kWh over night, so I can break even if I can generate just enough to export to cover the night-time charge of the batteries.
I haven't had them long enough to run through winter yet so we'll have to wait and see, but based on the end of this summer, I could probably cover the winter usage with export payback through summer at the current tariff rates when we were generating about 100% more than we were using per day.
I suspect the introductory tariff is far more generous than I'll have access to in a year's time when it expires though.
An odd thing about this article is that it ignores the deeper question: what balance of solar over-provisonioning + battery would most cost-effectively cover anticipated yearly needs?
I suspect that something like 3x'ing the solar (under 100k) would then let the author get away with much, much less battery, and result in a net cost savings.
Yeah seems like a relatively simple maths/econ problem to solve for, given some parameters like local solar power per m2 in the various seasons, electricity use in the various seasons and time of the day, and LCOE of solar and battery storage.
My guess is the differences in either choice aren't huge, as both solar and battery storage keeps getting cheaper.
Having an electric vehicle can really help, also. It basically soaks up excess solar power of an outsized installation during much of the year (making the payback time on the outsized installation very good), and can be charged away from the house during a few low-chance bad winter days when the outsized installation is enough to power the house but not the car. Electric cars are charged fully about 3 times per month on average in the US, so working around that with smart charging is not a complex challenge in the next decade.
The panels are the cheapest components. If you're incurring all the costs to retrofit your electrical panel with an inverter + batteries, you may as well implement on-site generation from the start to recoup more of the costs.
The thing is LFP or Sodium ion are both expected to have 5000+ useful cycles soon (or possibly even in production now). This means even if you use one full discharge overnight , this is like 15+ years of life of the battery, although I suspect calendar degradation will be much faster.
Higher the cycle life, lower the levelised cost of storage and this is what matters in my opinion. Best is to have some type of long term storage like a Diesel generator only for estimated 1-2 weeks of the year depending on location where it will be needed.
I feel V2G with 3 days backup and a house low power mode which can be utilised in emergencies might solve even this issue.
Oversizing solar to the extent possible for winter loads is also ideal because so far that does not seem to be the driving cost.
> Best is to have some type of long term storage like a Diesel generator only for estimated 1-2 weeks of the year depending on location where it will be needed.
Unless you live in a location without much sunlight, it’s better to invest in a solar powered system with a transfer switch to go off grid.
If you size the system appropriately it can recharge the battery by day during an outage and now you can operate off-grid for a very long time.
Diesel generators come with maintenance overhead that adds up year over year. They also contribute nothing during normal times, as opposed to a solar install which can offset electricity costs or even earn money.
If you live somewhere dark this is less helpful, though.
Consumption also matters. Some people have eye-popping amounts of electricity consumption while other households get by with far less. The difference, including heating and cooling costs, is surprisingly large between the highest and lowest households.
Something that isn't spoken about enough is that in developed Western countries, grids are actually significantly oversized due to reductions in electricity usage over time [1]. That link says 16% over, but the peak demand in the UK in 2024 was actually only 45MW [2], which I make more like a 30% reduction from the all-time peak.
Because of this, it feels like we should already have enough transmission capacity in a decent part of the network to cope with a re-organisation of where the sources and sinks are placed. Yes, we might need to do some work in the last mile, especially if V2G takes off, but things aren't nearly as bad as one might naively assume.
> in developed Western countries, grids are actually significantly oversized
Your sources really only apply to Britain and other deïndustrialising countries. American and European energy demand is rising due to electrification and AI.
It depends. In a neighboring county they have effectively saturated the grid and had to put a hold on datacenter permits. AI has been undoing a bunch of the efficiency savings we worked hard for in the past 20-30 years.
In case you didn't realize he is looking to store ALL of the summer generation into a battery and generate zero power in winter.. so rely entirely off of a battery during winter.. which is absolutely no feasible for a normal person and nobody would ever do.
Storing energy from the summer for the winter is a really inefficient way to do it. It's much better to massively over-provision the solar so you have enough energy - on average - for the winter. Then you only need a couple of week's worth of storage to account for extended cloudy periods.
Much cheaper, and you get a ton of extra free power in the summer. The only downside is a typical house roof doesn't have enough space. But a typical house doesn't have enough space for a 1 MWh battery either so...
Yup if you really need to be off grid in a climate that has cold, cloudy, snowy winters, you’re probably going to need a generator that runs on fossil fuels. For everyone else, use the grid.
Does anyone actually use generators for primary power rather than backup? Even the really nice Generac propane backups are crazy noisy. I was in a neighborhood on Cape Cod during a power outage and because about 1/3 of the houses had backup generators going it was unpleasant to be outside.
A 1 MWh battery isn't actually that big. There's electric trucks on the market right now with 600 kWh batteries sitting on the frame between the front and rear axle. That would easily fit into a basement room.
Off grid is silly unless you actually require it. Massive PV overprovision to ensure there's always something on the table is better than insane battery capacity. A couple of weeks worth of storage is a wild amount for a normal household.
I have a 22*980Ah 3.2Vn LiFePo4 array, and it holds a theoretical 13kWh at the 60% "safe" cycling rate (not below ~20%, not above ~80%, 3.0V min to 3.4V max). Taking DC->AC conversion losses into account, that ends up around 11kWh of 230VAC, which is enough for a single "normal" 24h period without generation: that doesn't include hoovering, welding, or running the dehydrator or dehumidifier. The batteries alone were USD$3500; BMS, balancer, cabling, etc. hundreds more. If I take $4000 as the unit price, then 14 days worth of power for us would represent $56k into a depreciating investment. I don't think most people are going to go for that. $56k would pay a lot of electric bills.
I'm in Ireland, which is fairly temperate, and we heat with wood (including the hot water). If you heat with electricity and you want to float that load on battery through a dim February...brutal.
EDIT: holy shitballs, that's $141,189.74 if you buy it as Powerwalls from Tesla rather than parts from Alibaba.
I live off grid in inland northern California, and a have a solar panel array large enough to run my air conditioner continuously while the sun is up. It's just large enough to run the blower for a gas furnace in the winter so sizing turned out to be pretty even. Using a heat pump in the winter would require several times larger panel array, and running it at night would require the battery be much, much larger.
My 5 kW solar array and 24 kWh battery is fine for my 1300 sq ft house, all summer long, even when it's cloudy, and it works great for clear winter days, but as you mentioned for extended days of bad weather, the battery runs empty. Fluffy white summer clouds aren't a problem, but thick winter rain clouds let in so littl light that the whole array can't even run a 200 W refrigerator, so a few days of rainy weather depletes the battery and I have to top it off with a generator.
If you have good TOU rates (some even offer free) it's far cheaper to skip solar and just get a battery - they are options for less than $100 / KWh. That's $1.5k for battery + inverter + 1-2 hours of labour. Equivalent solar system can cost 10x that.
That is what I did. 90kWp PV to power a house with 6000kWh yearly consumption. It works. And this was really cheap compared to buying expensive batteries that need replacing after 10 years. The 90kWp were about €90,000.00. I installed the modules and DC cabling/inverters myself and let the electrician handle the AC work.
One of the best ways to ensure you have energy is to reduce use and dependence. A huge amount of energy goes to heating and hot water so insulation and shorter showers with on demand can drastically reduce battery and solar panel needs.
> It's much better to massively over-provision the solar so you have enough energy - on average - for the winter.
Keep in mind that the UK is really far north, much farther north than most people expect, really, and the nights are really long in winter (there's up to 16 hours of night in London in December). And even your daylight hours aren't going to be sunny in average
So you'd have to over-provision a lot (like 10 or twenty times).
If you just want to come out cost neutral, the battery required is far smaller when paired with a large enough array, and a time-of-use tariff.
With 3 EV's in the house, and a 12.8kWp array, with a 10kWh battery, charging overnight in the winter on the cheap EV tariff (7p per kWh vs 27p per kWh) and exporting during the spring, summer and autumn at 15p per kWh I'm seeing an electricity bill of below 0.
Of course, with a shift in energy production to renewables, all of that maths may get upended, but for now, I'm going to break even far before my original estimates.
Another way to look at this: how much solar do you need to synthesize 1 MWh of methanol ("e-methanol") from water, which is only ~54 gallons (200 liters)? Actually you need 135 gallons since the generator is likely 40% efficient (or less..). This is not much fuel, I used to have two 275 gallon oil tanks in my basement.
I think e-methanol synthesis is ~%50% efficient, so double the solar. Doesn't sound so bad.
Now if you could synthesize methane you could push it into the gas grid and run the meters backwards, thereby avoiding the need for storage... actually methane synthesis is even more efficient, >70%.
If you consider the fact that only half of Earth is experiencing summer while the other half is experiencing winter, there's an obvious madlad solution to instead of storing power, transfer it from the summer hemisphere solar panels to the winter hemisphere electric heaters, somehow.
Can't shake the feeling that domestic PV is a con designed to try and shift responsibility for the climate crisis to consumers rather than industrial energy providers.
The ROI of a large PV farm must be substantially better than a home scale install.
Crashing panel prices, output degradation, local and state laws, and most importantly, bidirectional charging should all play into the long term calculations.
90 comments
[ 2.2 ms ] story [ 104 ms ] threadThe interesting impact will be on the grid itself. Why connect to the grid if you are self-sufficient?
Then the grid starts to degrade due to lack of maintenance, and the people that can't afford local storage become dependent essentially on a government maintained service.
Or should we be planning localized storage and grids at the same time, so we get the benefits of both scale and resiliency and redundancy.
People will be parking a mobile 100kWh battery at their house every night. We need integrated V2G and grid upgrades to make the most of this opportunity.
I grew up in Australia used to a grid averaging perhaps an hour’s downtime in the typical year. But now I live in India, and not only is the power frequently off for hours at a time (it’s a rare week that lacks an hour of downtime, and five or ten hours isn’t uncommon), the quality of the power is also far lower, and it damages hardware. It’s normal for AC units to need mildly expensive component replacements every year or two due to electrical damage, even with the obligatory voltage regulator in place, whereas in Australia I think most people never need to professionally service their AC until it completely packs up after maybe 15 years. If you’re going to want a decent-sized inverter and batteries anyway to get reliable power, then so long as you can get enough solar panellage, getting those solar panels and more batteries and going off-grid becomes mighty attractive—I suspect a payoff period of under a decade, even with comparatively cheap grid power, partly on the strength of electronics living longer.
—⁂—
Somewhere along the way, it actually becomes mandatory to be connected to such services. In Australia I lived in a rural town of under 100 people, and I asked if I could disconnect from the town water supply, and was told no. So that was some sum of mandatory daily connection fee for something that I would have preferred to unsubscribe from. (Town water was only hooked up to some outdoor taps, and the toilet; the supply had only become treated/potable five years prior, so every house was still hooked up to their rainwater tanks. In fact, the guy I bought the place from said that twenty years earlier you didn’t use the town water on your garden because it would kill the plants.)
- every household, can do that, _if_ they have a roof. appartment buildings may not have enough roof for all the people in it.
- for those who can't access that, (that includes people, but also the industry, your mobile phone provider, etc.) prices will get worse.
- the fire brigade will love industrial-size battery fires in the neighbourhood.
The answer is somewhere in the neighborhood of as much as one can safely store and afford accepting that batteries have a short life. Much like wells in cold climates the batteries should be in an underground insulated vault made from higher quality concrete as to keep fire hazards away from the home. That is also where whole-home generators and fuel belong, in their own vault so they can be easily maintained without having to rent an excavator to dig out the tank.
I think it's called a 'grid'.
Are there any other long term high density electric storage technologies that can fit in someones basement, garage, or even apartment closet?
https://youtu.be/JzdnUZReoLM?feature=shared
I suspect the answer is somewhere in the middle - maybe two weeks of storage. Though of course prices change all the time so the correct action will change and you need to rerun the numbers as things degrade to decide your next action.
2024:
May: 2494 kWh
Jun: 2323
Jul: 1915
Aug: 1634
Sep: 1008
Oct: 442
Nov: 185
Dec: 31
2025:
Jan: 43
Feb: 335
Mar: 980
Apr: 1510
My detached house has less space for solar panels than some smaller homes because all faces of the hip roof are triangular; lots of houses nearby that are semi's or terraced actually end up having more roof space because their roof faces are rectangular.
I managed to have 14x 465W panels total added on the east and south faces of my home, but the installer wanted an extra 40% of the total system price to add 5 more panels (and the 15th they couldn't fit on the south face, for 6 total on the west) because they'd have had to erect additional scaffolding and who knows what else. That was an absurd additional cost so we didn't do it, but that additional generation late into the afternoon would have been great for our peak usage at dinner time. My suspicion is they simply didn't want to do it, because the cost just doesn't add up.
On an overcast day at this time of year I can generate nearly enough to power the "baseline" of the house, but currently I receive 24p/kWh to sell the energy back, and I can charge the batteries at 15p/kWh over night, so I can break even if I can generate just enough to export to cover the night-time charge of the batteries.
I haven't had them long enough to run through winter yet so we'll have to wait and see, but based on the end of this summer, I could probably cover the winter usage with export payback through summer at the current tariff rates when we were generating about 100% more than we were using per day.
I suspect the introductory tariff is far more generous than I'll have access to in a year's time when it expires though.
I suspect that something like 3x'ing the solar (under 100k) would then let the author get away with much, much less battery, and result in a net cost savings.
My guess is the differences in either choice aren't huge, as both solar and battery storage keeps getting cheaper.
Having an electric vehicle can really help, also. It basically soaks up excess solar power of an outsized installation during much of the year (making the payback time on the outsized installation very good), and can be charged away from the house during a few low-chance bad winter days when the outsized installation is enough to power the house but not the car. Electric cars are charged fully about 3 times per month on average in the US, so working around that with smart charging is not a complex challenge in the next decade.
Higher the cycle life, lower the levelised cost of storage and this is what matters in my opinion. Best is to have some type of long term storage like a Diesel generator only for estimated 1-2 weeks of the year depending on location where it will be needed.
I feel V2G with 3 days backup and a house low power mode which can be utilised in emergencies might solve even this issue.
Oversizing solar to the extent possible for winter loads is also ideal because so far that does not seem to be the driving cost.
Unless you live in a location without much sunlight, it’s better to invest in a solar powered system with a transfer switch to go off grid.
If you size the system appropriately it can recharge the battery by day during an outage and now you can operate off-grid for a very long time.
Diesel generators come with maintenance overhead that adds up year over year. They also contribute nothing during normal times, as opposed to a solar install which can offset electricity costs or even earn money.
If you live somewhere dark this is less helpful, though.
Consumption also matters. Some people have eye-popping amounts of electricity consumption while other households get by with far less. The difference, including heating and cooling costs, is surprisingly large between the highest and lowest households.
https://enron.com/pages/the-egg?srsltid=AfmBOoqW03cqyIhQ0OlG...
Because of this, it feels like we should already have enough transmission capacity in a decent part of the network to cope with a re-organisation of where the sources and sinks are placed. Yes, we might need to do some work in the last mile, especially if V2G takes off, but things aren't nearly as bad as one might naively assume.
[1] https://www.nationalgrid.com/stories/journey-to-net-zero-sto...
[2] https://www.neso.energy/news/britains-electricity-explained-...
Your sources really only apply to Britain and other deïndustrialising countries. American and European energy demand is rising due to electrification and AI.
https://yle-fi.translate.goog/a/74-20138415?_x_tr_sl=auto&_x...
It was actually 1000 times that much.
They also test and publish yearly the latest battery combos.
Much cheaper, and you get a ton of extra free power in the summer. The only downside is a typical house roof doesn't have enough space. But a typical house doesn't have enough space for a 1 MWh battery either so...
I have a 22*980Ah 3.2Vn LiFePo4 array, and it holds a theoretical 13kWh at the 60% "safe" cycling rate (not below ~20%, not above ~80%, 3.0V min to 3.4V max). Taking DC->AC conversion losses into account, that ends up around 11kWh of 230VAC, which is enough for a single "normal" 24h period without generation: that doesn't include hoovering, welding, or running the dehydrator or dehumidifier. The batteries alone were USD$3500; BMS, balancer, cabling, etc. hundreds more. If I take $4000 as the unit price, then 14 days worth of power for us would represent $56k into a depreciating investment. I don't think most people are going to go for that. $56k would pay a lot of electric bills.
I'm in Ireland, which is fairly temperate, and we heat with wood (including the hot water). If you heat with electricity and you want to float that load on battery through a dim February...brutal.
EDIT: holy shitballs, that's $141,189.74 if you buy it as Powerwalls from Tesla rather than parts from Alibaba.
It's been done with heat. Using cheap electricity in the summer to generate heat and store it in basalt. There's a small block of houses in The Netherlands that gets their heat that way: https://www.ecodorpboekel.nl/basaltaccu-is-opgebouwd-uit-duu...
There's more systems like this around the world, although they use different storage methods.
https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...
My 5 kW solar array and 24 kWh battery is fine for my 1300 sq ft house, all summer long, even when it's cloudy, and it works great for clear winter days, but as you mentioned for extended days of bad weather, the battery runs empty. Fluffy white summer clouds aren't a problem, but thick winter rain clouds let in so littl light that the whole array can't even run a 200 W refrigerator, so a few days of rainy weather depletes the battery and I have to top it off with a generator.
Keep in mind that the UK is really far north, much farther north than most people expect, really, and the nights are really long in winter (there's up to 16 hours of night in London in December). And even your daylight hours aren't going to be sunny in average
So you'd have to over-provision a lot (like 10 or twenty times).
https://www.recurrentauto.com/research/winter-ev-range-loss
With 3 EV's in the house, and a 12.8kWp array, with a 10kWh battery, charging overnight in the winter on the cheap EV tariff (7p per kWh vs 27p per kWh) and exporting during the spring, summer and autumn at 15p per kWh I'm seeing an electricity bill of below 0.
Of course, with a shift in energy production to renewables, all of that maths may get upended, but for now, I'm going to break even far before my original estimates.
I think e-methanol synthesis is ~%50% efficient, so double the solar. Doesn't sound so bad.
Now if you could synthesize methane you could push it into the gas grid and run the meters backwards, thereby avoiding the need for storage... actually methane synthesis is even more efficient, >70%.
which being very approximate is 15k gbp/year
The ROI of a large PV farm must be substantially better than a home scale install.