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I don't have good aggregate data on energy spent, but the relative expense is actually easy to understand since it mostly just comes down to the delta in temper

I don't have good aggregate data on energy spent, but the relative expense is actually easy to understand since it mostly just comes down to the delta in temperature you're trying to achieve. In a moderately hot climate you may want to lower the temp 10-20 deg c, for example, from from 38 to 23c (~100 to 73f). In a moderately cold climate you may want to raise the 25-35 deg c, for example from -10 to 22c (~14 to 72f). The latter requires about twice as much energy as the former. There's a common meme in the northern latitudes that people "down south" consume unreasonable amounts of energy on AC, but in many cases northern cities consume more energy in winter than southern cities do in summer. The truth is that just about every city uses large amounts of energy for climate control, and the actual expense varies more by microclimate than by latitude. There are only a few places on earth where people consume very little climate control, and those places tend to already be densely populated because "they're nice."

frosted-flakes 5y ago
The difference is that most people heat their homes with gas or oil, which is significantly cheaper than electric heaters (heat pump or otherwise) and for some reason isn't considered as energy the same way electricity is. Air conditioners/heat pumps can only use electricity, and they use quite a lot of it.
- deleted 5y ago
  [deleted]
- rootusrootus 5y ago
  > isn't considered as energy the same way electricity is That is a good point, I think you're exactly right. I just tried to figure out how many kWh is equivalent to a therm of natural gas, and the answer of course is 'it depends.' In round numbers it seems like 1 therm is about 30 kWh. Using myself as an example, during a cold month I might use about 90 therms. In a hot month I may use 1900 kWh for cooling. Gas is significantly cheaper indeed, though it's noticeably more energy (and that's after converted to hypothetical electricity, not the energy content of the raw gas). What a PITA to compare that. And it's a pretty rough comparison, indeed, because gas is predominantly going for heat in the winter, but I have a gas stove and a gas water heater too. And I have an electric car, which pushes the kWh total up a bit. I'd have to do a much more detailed analysis if I actually wanted to compare the energy usage.
- crazygringo 5y ago
  Gas/oil is definitely cheaper than electric heaters, but I thought these days heat pumps were cheaper than gas/oil, at least until you got down to temperatures below ~10°F? Because heat pumps are now so efficient, all the new apartment construction I see in NYC uses them. (While older buildings use dirty oil to heat water for radiators.)
  - stormbrew 5y ago
    Heat pumps definitely shouldn't be lumped in with resistive heating (which is what I think of when I think of "electric heaters"). They are definitely more energy efficient than either resistive or gas/oil, but whether they're cheaper depends on the relative cost of local electricity and gas delivery. Gas is still often cheaper than electicity, so it really depends on your goal: energy efficiency/carbon output vs. cost efficiency. My money is on "gas won't be cheaper for much longer, even where it is now" personally, though.
rootusrootus 5y ago
> mostly just comes down to the delta in temperature Ah yes, this is a very good point, that does make it much easier to conceptualize.
nkozyra 5y ago
> There's a common meme in the northern latitudes that people "down south" consume unreasonable amounts of energy on AC, but Depending on where "down south" you are, the AC could well be on eleven months of the year. I'm in Florida now, and you can usually turn it off for parts of November - February but never every day. I'd average it at 10 months of ac usage in a year When I was in NYC, the ac would be used for about 1.5 months and the heat for ~ 3. By being temperate in spring, early summer and fall, little or no external energy needed.
- BizarroLand 5y ago
  I live in the PNW and heat dome notwithstanding very few homes have AC because it almost never gets above 90ish degrees in the summer. A good cross breeze is more than sufficient to keep cool in that case. Winters, though, need a lot of heating to keep the place comfortable and most homes due to lack of said AC use the highly inefficient baseboard heaters to warm their entire house 6 months or more out of the year.
  - rootusrootus 5y ago
    > very few homes have AC That's actually not correct, though I would have figured the same thing myself before the recent heat wave made it a discussion point. Seattle is among the lowest in the nation, but it's still just under half of all homes. Portland is about three quarters.
  - nkozyra 5y ago
    I just spent awhile in Oregon (yes even during the heat wave) and will agree evenings with a breeze were totally fine even on the hottest days. The 110°+ felt a lot like Florida when it's 92 and humid
  - Supermancho 5y ago
    > I live in the PNW and heat dome notwithstanding very few homes have AC because it almost never gets above 90ish degrees in the summer. I lived in the greater Seattle area in the last 4 years. Let's look at the top temps for the last couple years in Seattle - the bounds of the city, which is literally bordering the bay. 98 August 16, 2020 95 June 12, 2019 94 August 08, 2018 96 June 25, 2017 95 August 19, 2016 95 July 19, 2015 Not counting EXACTLY in Seattle you routinely break 100F in the greater Seattle Area and Washington State. Let's look at Spokane 102 July 31, 2020 98 August 07, 2019 103 August 09, 2018 99 July 07, 2017 These are hottest days, not the only days of over 90. Remember the forest fires of the last couple years, it generated the WA memes about deciding if you want to cool your house by opening a window or avoid the billowing smoke that comes in.
pdonis 5y ago
> it mostly just comes down to the delta in temperature you're trying to achieve Not for cooling; cooling also requires condensing excess water vapor out of the air (since the dewpoint of the cooled air is much lower than the dewpoint of the air before you started cooling it). Most of the energy expenditure for A/C is actually condensing water vapor, not cooling air. Air has a very low heat capacity compared to water (particularly water during the phase change from vapor to liquid). Off the top of my head I think costs about 6 times as much energy to condense water vapor as to cool the air for typical A/C conditions; if that number is roughly correct, then for the temperature differences you give, heating actually uses about 2/7 (about 30%) of the energy of cooling (if we let the energy required to cool the air be 1, then the energy required to heat the air is 2, but the energy required to condense water vapor is 6, so the total cooling energy is 7.)
- crazygringo 5y ago
  Do you have a reputable source for that? I've never heard that before, it seems to defy intuition in a couple of ways, and it defies my own electricity bill. First, water vapor in air is usually less than 2% of air by mass, and contrary to what you say there's absolutely no phase change involved -- water vapor isn't steam, it's far far below boiling. And AC usually doesn't condense more than about 25% of humidity, so it's really a tiny, tiny amount of water being cooled relative to air being cooled. So I'm missing what could possible be so energy-intensive about cooling water vapor, or why condensation would be relevant to energy usage at all? (Cool condensation still helps "chill" the room.) And second, even if that were the case, wouldn't it be the identical energy loss when heating? A heat pump in the winter is literally just air-conditioning the outside, and produces similar condensation in the unit outdoors. In fact, my heat pump runs in reverse for ~15 min once or twice a day on really cold days (suddenly it blows cold air inside and warm air outside) in order to melt the accumulated ice from condensation, to continue operating safely. So I don't see at all how how cooling somehow uses 3.5x more energy than heating. My personal electric bill with my heat pump is also about 2x as expensive in the coldest winter months (heating from 25°F to 70°F = +45°F) as in the warmest summer months (cooling from 90°F to 70°F = -20°F). If your math were correct, it would be roughly the opposite. As far as I can tell, the cost of running a heat pump is basically the same no matter which direction you're running it.

frosted-flakes 5y ago

The difference is that most people heat their homes with gas or oil, which is significantly cheaper than electric heaters (heat pump or otherwise) and for some reason isn't considered as energy the same way electricity is. Air conditioners/heat pumps can only use electricity, and they use quite a lot of it.

deleted 5y ago
[deleted]
rootusrootus 5y ago
> isn't considered as energy the same way electricity is That is a good point, I think you're exactly right. I just tried to figure out how many kWh is equivalent to a therm of natural gas, and the answer of course is 'it depends.' In round numbers it seems like 1 therm is about 30 kWh. Using myself as an example, during a cold month I might use about 90 therms. In a hot month I may use 1900 kWh for cooling. Gas is significantly cheaper indeed, though it's noticeably more energy (and that's after converted to hypothetical electricity, not the energy content of the raw gas). What a PITA to compare that. And it's a pretty rough comparison, indeed, because gas is predominantly going for heat in the winter, but I have a gas stove and a gas water heater too. And I have an electric car, which pushes the kWh total up a bit. I'd have to do a much more detailed analysis if I actually wanted to compare the energy usage.
crazygringo 5y ago
Gas/oil is definitely cheaper than electric heaters, but I thought these days heat pumps were cheaper than gas/oil, at least until you got down to temperatures below ~10°F? Because heat pumps are now so efficient, all the new apartment construction I see in NYC uses them. (While older buildings use dirty oil to heat water for radiators.)
- stormbrew 5y ago
  Heat pumps definitely shouldn't be lumped in with resistive heating (which is what I think of when I think of "electric heaters"). They are definitely more energy efficient than either resistive or gas/oil, but whether they're cheaper depends on the relative cost of local electricity and gas delivery. Gas is still often cheaper than electicity, so it really depends on your goal: energy efficiency/carbon output vs. cost efficiency. My money is on "gas won't be cheaper for much longer, even where it is now" personally, though.

rootusrootus 5y ago

> mostly just comes down to the delta in temperature Ah yes, this is a very good point, that does make it much easier to conceptualize.

nkozyra 5y ago

> There's a common meme in the northern latitudes that people "down south" consume unreasonable amounts of energy on AC, but Depending on where "down south" you are, the AC could well be on eleven months of the year. I'm in Florida now, and you can usually turn it off for parts of November - February but never every day. I'd average it at 10 months of ac usage in a year When I was in NYC, the ac would be used for about 1.5 months and the heat for ~ 3. By being temperate in spring, early summer and fall, little or no external energy needed.

BizarroLand 5y ago
I live in the PNW and heat dome notwithstanding very few homes have AC because it almost never gets above 90ish degrees in the summer. A good cross breeze is more than sufficient to keep cool in that case. Winters, though, need a lot of heating to keep the place comfortable and most homes due to lack of said AC use the highly inefficient baseboard heaters to warm their entire house 6 months or more out of the year.
- rootusrootus 5y ago
  > very few homes have AC That's actually not correct, though I would have figured the same thing myself before the recent heat wave made it a discussion point. Seattle is among the lowest in the nation, but it's still just under half of all homes. Portland is about three quarters.
- nkozyra 5y ago
  I just spent awhile in Oregon (yes even during the heat wave) and will agree evenings with a breeze were totally fine even on the hottest days. The 110°+ felt a lot like Florida when it's 92 and humid
- Supermancho 5y ago
  > I live in the PNW and heat dome notwithstanding very few homes have AC because it almost never gets above 90ish degrees in the summer. I lived in the greater Seattle area in the last 4 years. Let's look at the top temps for the last couple years in Seattle - the bounds of the city, which is literally bordering the bay. 98 August 16, 2020 95 June 12, 2019 94 August 08, 2018 96 June 25, 2017 95 August 19, 2016 95 July 19, 2015 Not counting EXACTLY in Seattle you routinely break 100F in the greater Seattle Area and Washington State. Let's look at Spokane 102 July 31, 2020 98 August 07, 2019 103 August 09, 2018 99 July 07, 2017 These are hottest days, not the only days of over 90. Remember the forest fires of the last couple years, it generated the WA memes about deciding if you want to cool your house by opening a window or avoid the billowing smoke that comes in.

pdonis 5y ago

> it mostly just comes down to the delta in temperature you're trying to achieve Not for cooling; cooling also requires condensing excess water vapor out of the air (since the dewpoint of the cooled air is much lower than the dewpoint of the air before you started cooling it). Most of the energy expenditure for A/C is actually condensing water vapor, not cooling air. Air has a very low heat capacity compared to water (particularly water during the phase change from vapor to liquid). Off the top of my head I think costs about 6 times as much energy to condense water vapor as to cool the air for typical A/C conditions; if that number is roughly correct, then for the temperature differences you give, heating actually uses about 2/7 (about 30%) of the energy of cooling (if we let the energy required to cool the air be 1, then the energy required to heat the air is 2, but the energy required to condense water vapor is 6, so the total cooling energy is 7.)

crazygringo 5y ago
Do you have a reputable source for that? I've never heard that before, it seems to defy intuition in a couple of ways, and it defies my own electricity bill. First, water vapor in air is usually less than 2% of air by mass, and contrary to what you say there's absolutely no phase change involved -- water vapor isn't steam, it's far far below boiling. And AC usually doesn't condense more than about 25% of humidity, so it's really a tiny, tiny amount of water being cooled relative to air being cooled. So I'm missing what could possible be so energy-intensive about cooling water vapor, or why condensation would be relevant to energy usage at all? (Cool condensation still helps "chill" the room.) And second, even if that were the case, wouldn't it be the identical energy loss when heating? A heat pump in the winter is literally just air-conditioning the outside, and produces similar condensation in the unit outdoors. In fact, my heat pump runs in reverse for ~15 min once or twice a day on really cold days (suddenly it blows cold air inside and warm air outside) in order to melt the accumulated ice from condensation, to continue operating safely. So I don't see at all how how cooling somehow uses 3.5x more energy than heating. My personal electric bill with my heat pump is also about 2x as expensive in the coldest winter months (heating from 25°F to 70°F = +45°F) as in the warmest summer months (cooling from 90°F to 70°F = -20°F). If your math were correct, it would be roughly the opposite. As far as I can tell, the cost of running a heat pump is basically the same no matter which direction you're running it.