Heat is many times more expensive than air conditioning expecially in temperate climates too cold for heat pumps during winter. It's one scenario where global warming will actually decrease energy usage.
Well it is also political/rhetorical to some degree. Air conditioning is energy inefficient while heating technically starts with a 100% conversion efficiency. You also can't say 'just don't use heat' without looking idiotic and out of touch.
Meanwhile air conditioning is considered a luxury even if lack of it also results in people dying - both are of course on a spectrum in terms of necessity depending on circumstances.
> Air conditioning is energy inefficient while heating technically starts with a 100% conversion efficiency.
This is a common misconception- electrically resistive heat generation is not the most efficient way to heat a room with electricity. Rather, you can move about two to three times more heat per unit energy using a heat pump than you can with simple resistive heating.
Thermodynamics, specifically the second law, certainly makes it so. Some of the electronics utilize the energy and thus work is performed, and not all energy is wasted out as heat, nor is all utilized energy perfectly converted into heat.
Heat pumps are the most effective way of cooling or heating something as long as you have good insulation and the temperature range is within the effective range in which the pump can operate.
This is why you get over 100% efficiency in terms of work vs output.
Say you have a 100% efficient heater it means for every watt you put in a watt of heat is released to the environment.
A heat pump doesn’t releases anything it moves it from one side to another so for one watt of energy that it takes to operate a heat pump you can move up to 10 watts worth of heat (some pumps can be even more efficient than this) form one side to another.
I'm no expert, but I think AC is generally far in excess of 100% efficient. The relevant number is the SEER rating, which is the ratio between the rate of cooling and the power draw. Typical SEER ratios are 10 or higher, for an efficiency in excess of 1000%.
> Air conditioning is energy inefficient while heating technically starts with a 100% conversion efficiency.
This is a common misconception. AC is far above 100% efficiency because it moves heat rather than creating it. Maintaining a 30 degree temperature difference (say 40->70F) using traditional heat is far more energy demanding than air conditioning from 100->70F. The difference is big enough that HVAC costs in a scorching desert climate like Dubai are lower than much of northern Europe.
Heat pump based heating moves heat like AC, but efficiency drops the greater the temperature difference between inside and outside. Most cold climates are too cold for heat pumps to work for much of the year. On the other hand even the hottest climates don't have a temperate Delta of more than 40F inside to outside on the hottest days. So air conditioning is still in the efficient heat pump operating band.
Heat via natural gas is far cheaper than air conditioning via electricity in all parts of the US, as far as I’m aware. And cheaper by a wide margin.
Electricity costs due to AC are typically at least 3x more in the summer than gas costs due to heating.
Edit: I shouldn’t have written all parts of the US, but wherever you’re trying to bring temperatures down just as much as you’re trying to bring them up in winter.
Depends on the temperature differential between the outside air and the climate controlled environment. Here, in eastern Washington, winter costs me a lot more. Using the shoulder season as a baseline, summer adds x and winter adds 3x.
I have gas heat and electric a/c and my bill is significantly higher in winter. I live near San Jose, which can reach the 90s in summer and the 40s in winter.
I should have clarified that I meant in locales where you might need to cool just as much as you heat, and probably also applies to places with higher humidity than west coast, since there is more need to use AC when it’s more humid.
32C (90F) doesn't necessarily need AC yet though? At least if the nights are clearly cooler, so that the windows can be shaded at daytime and opened at night. In an old stone house this can work still at over 40C (104F), depending a lot on the general shading etc of course.
Depends a ton on humidity. In a humid area like deep South or Midwest 90F is extremely uncomfortable. In a desert climate like SoCal 90 isn't bad in the shade, and not even uncomfortable with fans
Yeah, what most people don't know is that AC is a great dehumidifier along with cooling. The air gets pretty cold right when it passes over the coils. Cold air holds less water, so a lot of humidity drops out as condensate. A lot of cooling power is actually consumed by the vapor->liquid transition of water in the air. This is why it's very important to have a well sealed house when using heat pumps/ac. Letting more water vapor in is just as bad as letting in warmerr air. Once the humidity is lowered the AC unit doesn't work nearly as hard to cool air
The cold feeling is two fold. The lower humidity helps almost as much as the temperature drop in humid areas.
Heating doesn't cause the water vapor phase transition so sealing out humid air matters little for efficiency. This is why many older buildings have higher cooling than heating costs. Sealing is just as important as insulation when cooling
Hmm. The coefficient of a properly installed ground or water source heat pump can hit 4 or 5. Which means for each kw of power driving the contraption, up to 5kw of heating or cooling comes out. They're not creating heat, but moving it from one place to another. Air source is rather less, not sure of the figures.
There's no reason a heat pump can't heat a house and water as well as cooling it. Gas doesn't even run at 100% efficiency as some of that heat is disappearing out the flue.
So unless gas is under a quarter of the price of electricity it should pay, and pay well...
I found the source of confusion. I was under the assumption that a heat pump and electrical resistance heating were the same thing. But they are not, however, a heat pump is never used in actually cold places, because:
>In most cases, an experienced HVAC technician will opt to install a furnace over a heat pump if they have access to natural gas. The exception to this is when a home is located in the coastal areas of California and the gulf states.
>Because heat pumps are transferring heat from one area to another, what happens if it is -20 degrees outside in the middle of a North Dakota winter? Is there any heat to transfer into your house? That’s the catch.
>A heat pump only works well if the temperature is above freezing, and is almost useless in the middle of a harsh northern winter. Ideally a heat pump is used when the temperature outside is over 40-50 degrees fahrenheit (and are VERY inefficient below 30-32 degrees), so heat pumps are out if you live in Montana unless you also have a supplemental means of heating your house. In fact, heat pumps are actually designed for coastal climates in the southern states. So what do people in Bozeman, Montana do? They use a furnace, or a wood-burning stove!
That page is talking total crap. Must be trying to sell you a furnace!
Heat pumps are pretty common in Scandinavia, and readily available in Canada and other cold places. I found this on a Canada gov website: "At –8.3°C, the COP is typically 2.3". So at 17°F in American money, that's 2.3kW out for every 1kW in, and air source is the least efficient type.
Heat pumps for heating do degrade in efficiency as temperature drops, but stay cost effective down to -15°C, or -20°C or so. Supposedly, newer ones go even lower still. With ground source you just dig a bit deeper, as assuming we're not talking permafrost it's fairly easy to reach efficient temperatures.
Huh, looks like I have more to learn. I’ve only ever seen gas furnaces used to heat wherever there is gas supply available in the US (Northeast/Midwest/Pacific Northwest). Heat pump is only used as air conditioner if gas available. I assumed this was because it’s not possible or efficient to operate a heat pump in colder temperatures.
Mainly cost I'd say. 20 or 40 years ago, depending where you were, gas was cheap enough that it mostly wasn't worth caring that much, and electric anything was the expensive option. Aircon for cooling was a much easier choice. These days it's starting to look hugely attractive both ways, and I think will be ever more so.
Cold areas usually have a mostly unused backup heater in heat pumps, for those few times record breaking cold arrives, and of course the nearer you get to a COP of 1 (1kW in = 1kW out) the longer it takes to pay back the extra cost.
I'm guessing you have an older HVAC system. Huge advances in air source heat pump efficiency came in the last decade. If you own the place and plan to stay there more than ~5 years I would look into it. Could save you a lot over time depending on local climate.
Gas heat is cheaper than ever. But as long as you're not in an extremely cold area heat pump is probably cheaper. In your case, it might make sense to keep the furnace for days too cold for the heat pump to work efficiently. Use it as supplemental heat.
In days when temperatures are >40F the heat pump would be ~6X more efficient at moving BTU than gas heat. You can use online calculator to work out the BTU of gas used vs electricity cost. There's definitely a lower temp limit where gas is cheaper, but also a good chance your climate doesn't hit that temp often
The temperature delta will be less since most of the earth is "cold" relative to human preference. We're one of the least cold tolerant species without artificial clothing. Pretty much evolved for the tropics
Technically true for cooling as well, thete exist gas powered AC systems (and fridges etc). You could slso use mechanical sources such as water mill or windmill to power the compressor but there probably aren't commercial systems on the market.
Au contraire! Cooling is much more difficult than heating (the same number of degrees obviously) because of the waste heat of the device itself. The relevant technical term is exergy loss stream.
Rising energy usage is an invariant. If it weren't for an increased demand for air conditioning, it would be for an an increased demand in other areas - transportation, computing, desalination, etc.
The answer is not to try to stop development - the answer is to cleanse the sources of electricity.
If electric cars become more popular, they're going to dwarf any other household use anyway. A Tesla's batteries already hold more energy than the average household uses in a weekend.
I'd estimate a driving range with the electricity consumption of an average 4-person household (4000 kWh/year in Germany) of at least 20k km (@ 20 kWh/100 km). So that would roughly double the household use.
Add another 4000 kwh for heating around 50-150 m² (90-25 kWh/m² per year for a modern home in Germany).
In Germany you can use about 1.000 kWh/kWp per year from the sun, so one would need to install 60 m² of panels @ 20% efficiency for that.
The main problem is storage for the winter - or where am I wrong?
"Stop development" is a bit of an alarmist phrase. Few want that. Also, reducing demand in specific areas is still beneficial even if overall demand continues to increase. There's no reason not to address both demand and supply.
Tough one. Let me think a moment. Hey, didn't I just read an article about how air conditioning represented a significant amount of unnecessary energy use? Crazy idea: let's reduce that. While we're at it, maybe we could also do things to reduce the number of cars on the road, or increase efficiency. We could build stuff using materials and processes that are less energy-intensive. There are a hundred other ways we could reduce the number of kWh used per day, separately from changing how those kWh are generated.
If you lived in a hot climate (like India, which is one of the countries TFA referred to as a source of high future demand), then you'd understand just how crazy of an idea that is. (side note: your profile links to a site with a bio claiming that you live in Massachusetts. I rest my case.)
Look, it's not that the idea has zero merit. There are architectures which do a better job at keeping the interiors cool, and incentives could be set up to favor those designs. But such designs are also usually bone-cold in the winter, and you see energy usage pendulum-swing back to high in other parts of the year. Plus, locales with hot weather typically have local architectures with these kinds of "natural cooling" features anyway, so it's usually not anything new.
There's a reason why I think calls to reduce air conditioning to be anti-development, and it's because I happen to live in one of said climates, and there's no way I'd get anything done without air conditioning. Unless we want to keep the underdeveloped regions of the world in poverty, increased demand for air conditioning is simply inevitable.
There is some overlap as the article mentions. There's also a synergistic secondary effect of residential solar not mentioned by the article: PV panels on your roof shade your house and the solar energy that was heating your house is now cooling it.
But the overlap is not perfect. Typically the hottest part of the day is a few hours after solar peak, and it's often still hot after the sun goes down. So you still need storage and/or grid power for complete A/C coverage.
With sufficiently good insulation (see passive houses in cold climates), the house should follow the outdoor temperature quite slowly and not change much over the day.
Insulation, or thermal mass - this is why adobe and rammed earth are suitable building materials for hot climates: thick walls take a lot of time to heat up and cool down and help to stabilise the inside climate.
There is obviously some correlation between high insolation and high temperature, but peak temperature and peak insolation don't happen at the same time of day (peak insolation is solar noon; peak temperature often comes hours later), and insolation is far from the only factor that determines how much AC is needed.
Could a partial answer to the power question be a large-scale bike system merging the power from people pedaling (probably some hydraulics in there) to drive a generator?
It seems that people could burn a few calories and generate substantial kilowattage with a bit of clever engineering.
Same concept applied to an Archimedes pump bringing seawater to the top of a gravity-driven reverse-osmosis purification plant could increase arable land.
We built a setup like this where four people would power a monitor with sound and a small video player to show short movies like Big Buck Bunny.
The point was to demonstrate how utterly inefficient this power generation method is.
So, by the time enough people were put in parallel, the problem would move to maintaining literally hundreds of bicycle devices, swapping out crews of sweaty bodies with fresh meat, and then keeping everyone hydrated and medically fit.
I just had to point out that a similar idea was incorporated in the second episode of Black Mirror. It's one of my favorite shows, don't know if you're a fan.
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[ 3.2 ms ] story [ 38.4 ms ] threadMeanwhile air conditioning is considered a luxury even if lack of it also results in people dying - both are of course on a spectrum in terms of necessity depending on circumstances.
This is a common misconception- electrically resistive heat generation is not the most efficient way to heat a room with electricity. Rather, you can move about two to three times more heat per unit energy using a heat pump than you can with simple resistive heating.
https://en.wikipedia.org/wiki/Heat_pump
This is why you get over 100% efficiency in terms of work vs output.
Say you have a 100% efficient heater it means for every watt you put in a watt of heat is released to the environment.
A heat pump doesn’t releases anything it moves it from one side to another so for one watt of energy that it takes to operate a heat pump you can move up to 10 watts worth of heat (some pumps can be even more efficient than this) form one side to another.
https://www.engineeringtoolbox.com/air-conditioner-efficienc...
> you also can't say 'just don't use heat' without looking idiotic
Can't you put on a sweater to minimize your energy footprint?
> air conditioning is considered a luxury
Isn't air conditioning common even in developing countries? Perhaps it is luxurious to cool your environment, but to what extent is it a luxury?
> even if lack of it also results in people dying
Are people dying from lack of air conditioning? Will people die without it? I find it is difficult to argue causation of death due to lack of a luxury
https://en.m.wikipedia.org/wiki/2003_European_heat_wave
This is a common misconception. AC is far above 100% efficiency because it moves heat rather than creating it. Maintaining a 30 degree temperature difference (say 40->70F) using traditional heat is far more energy demanding than air conditioning from 100->70F. The difference is big enough that HVAC costs in a scorching desert climate like Dubai are lower than much of northern Europe.
Heat pump based heating moves heat like AC, but efficiency drops the greater the temperature difference between inside and outside. Most cold climates are too cold for heat pumps to work for much of the year. On the other hand even the hottest climates don't have a temperate Delta of more than 40F inside to outside on the hottest days. So air conditioning is still in the efficient heat pump operating band.
Electricity costs due to AC are typically at least 3x more in the summer than gas costs due to heating.
Edit: I shouldn’t have written all parts of the US, but wherever you’re trying to bring temperatures down just as much as you’re trying to bring them up in winter.
The cold feeling is two fold. The lower humidity helps almost as much as the temperature drop in humid areas.
Heating doesn't cause the water vapor phase transition so sealing out humid air matters little for efficiency. This is why many older buildings have higher cooling than heating costs. Sealing is just as important as insulation when cooling
There's no reason a heat pump can't heat a house and water as well as cooling it. Gas doesn't even run at 100% efficiency as some of that heat is disappearing out the flue.
So unless gas is under a quarter of the price of electricity it should pay, and pay well...
>In most cases, an experienced HVAC technician will opt to install a furnace over a heat pump if they have access to natural gas. The exception to this is when a home is located in the coastal areas of California and the gulf states.
>Because heat pumps are transferring heat from one area to another, what happens if it is -20 degrees outside in the middle of a North Dakota winter? Is there any heat to transfer into your house? That’s the catch.
>A heat pump only works well if the temperature is above freezing, and is almost useless in the middle of a harsh northern winter. Ideally a heat pump is used when the temperature outside is over 40-50 degrees fahrenheit (and are VERY inefficient below 30-32 degrees), so heat pumps are out if you live in Montana unless you also have a supplemental means of heating your house. In fact, heat pumps are actually designed for coastal climates in the southern states. So what do people in Bozeman, Montana do? They use a furnace, or a wood-burning stove!
https://asm-air.com/hvac/heat-pump-vs-furnace-pros-cons/
Heat pumps are pretty common in Scandinavia, and readily available in Canada and other cold places. I found this on a Canada gov website: "At –8.3°C, the COP is typically 2.3". So at 17°F in American money, that's 2.3kW out for every 1kW in, and air source is the least efficient type.
https://www.nrcan.gc.ca/energy/publications/efficiency/heati...
Heat pumps for heating do degrade in efficiency as temperature drops, but stay cost effective down to -15°C, or -20°C or so. Supposedly, newer ones go even lower still. With ground source you just dig a bit deeper, as assuming we're not talking permafrost it's fairly easy to reach efficient temperatures.
Cold areas usually have a mostly unused backup heater in heat pumps, for those few times record breaking cold arrives, and of course the nearer you get to a COP of 1 (1kW in = 1kW out) the longer it takes to pay back the extra cost.
Gas heat is cheaper than ever. But as long as you're not in an extremely cold area heat pump is probably cheaper. In your case, it might make sense to keep the furnace for days too cold for the heat pump to work efficiently. Use it as supplemental heat.
In days when temperatures are >40F the heat pump would be ~6X more efficient at moving BTU than gas heat. You can use online calculator to work out the BTU of gas used vs electricity cost. There's definitely a lower temp limit where gas is cheaper, but also a good chance your climate doesn't hit that temp often
Doesn't climate change lead to extreme temperatures in both directions though?
The answer is not to try to stop development - the answer is to cleanse the sources of electricity.
Add another 4000 kwh for heating around 50-150 m² (90-25 kWh/m² per year for a modern home in Germany).
In Germany you can use about 1.000 kWh/kWp per year from the sun, so one would need to install 60 m² of panels @ 20% efficiency for that.
The main problem is storage for the winter - or where am I wrong?
"Stop development" is a bit of an alarmist phrase. Few want that. Also, reducing demand in specific areas is still beneficial even if overall demand continues to increase. There's no reason not to address both demand and supply.
If you lived in a hot climate (like India, which is one of the countries TFA referred to as a source of high future demand), then you'd understand just how crazy of an idea that is. (side note: your profile links to a site with a bio claiming that you live in Massachusetts. I rest my case.)
Look, it's not that the idea has zero merit. There are architectures which do a better job at keeping the interiors cool, and incentives could be set up to favor those designs. But such designs are also usually bone-cold in the winter, and you see energy usage pendulum-swing back to high in other parts of the year. Plus, locales with hot weather typically have local architectures with these kinds of "natural cooling" features anyway, so it's usually not anything new.
There's a reason why I think calls to reduce air conditioning to be anti-development, and it's because I happen to live in one of said climates, and there's no way I'd get anything done without air conditioning. Unless we want to keep the underdeveloped regions of the world in poverty, increased demand for air conditioning is simply inevitable.
(If the article covered this, my apologies - I couldn't read the whole thing without having to pay).
But the overlap is not perfect. Typically the hottest part of the day is a few hours after solar peak, and it's often still hot after the sun goes down. So you still need storage and/or grid power for complete A/C coverage.
It seems that people could burn a few calories and generate substantial kilowattage with a bit of clever engineering.
Same concept applied to an Archimedes pump bringing seawater to the top of a gravity-driven reverse-osmosis purification plant could increase arable land.
Sounds like we're several innovations away.
Let's put Elon Musk on the task.
https://en.wikipedia.org/wiki/Fifteen_Million_Merits