5 ms·

> let's not forget that the point of switching to electricity is to be able to use renewables Here in the UK, natural gas is used to provide electricity[1], so

by rlpb 2y ago

> let's not forget that the point of switching to electricity is to be able to use renewables Here in the UK, natural gas is used to provide electricity[1], so switching to a heat pump right now isn't likely to help with the environment and (because gas is vastly cheaper per unit energy) nor the utility bill. You might as well spend the capex on the insulation upgrades required for a heat pump anyway, but then stay on gas. The bottleneck seems to be on us weaning ourselves off gas for electricity first. [1] 53% natural gas during the recent cold snap, and only 16% renewables, according to https://news.sky.com/story/britains-gas-storage-levels-concerningly-low-after-cold-snap-13286305 https://news.sky.com/story/britains-gas-storage-levels-conce...

harg 2y ago
You get more heat out of using a given quantity of gas to generate electricity which is used to to power a heat pump than you do by burning the gas directly for heat, even when considering generation and transmission losses etc. Given that even during a time of low output from renewables we still only rely on 53% gas for electricity generation it's still much more beneficial environmentally to use a heat pump. The monetary cost is another story though, and I agree we do need to work on weaning ourselves off gas.
- StillBored 2y ago
  In areas with moderate outdoor temperatures. Anywhere that the heatpump is going through defrost cycles, that statement is likely false because the COP is likely 1 or less when that starts happening. Then on the generation side, its worse if the NG generation isn't a modern combined cycle plant. which also tends to nix places with a lot of renewable generation because the NG plants are just peaker gas turbines with much lower efficiency than plants designed for continuous use. So, its all situational, but at the same time if one has the choice for cheap NG using that as a second stage and setting the crossover heatpump temperature at the cost/BTU intersection between the heatpump and NG second stage is a rough approximation of the enviromental costs as well as the actual cost.
  - triceratops 2y ago
    > In areas with moderate outdoor temperatures. Anywhere that the heatpump is going through defrost cycles, that statement is likely false because the COP is likely 1 or less when that starts happening. Modern heat pumps have a COP close to 2 at 5F/-15C while still delivering 50k+ BTUs. Here's one example: https://ashp.neep.org/#!/product/68628/7/25000/95/7500/0///0 https://ashp.neep.org/#!/product/68628/7/25000/95/7500/0///0
    - StillBored 2y ago
      While heating, That isn't even a particularly efficient unit (EER 9), and not all all unusual for r410 (which is basically banned for new sales in the USA since jan 1st) But it has a 150W pan heater, but I don't think that is its primary defrost mode, at least its not going to be at 50k btu at those temperatures unless its also really dry. The pan heater is probably to just assure that the coil melt water doesn't build up in the base pan. For most of the forced air systemms in the USA, the deforst mode is as I mentioned triggered via outdoor coil temp/runtimes and somewhere below an ambient of ~30F, which will be a coil temp of ~20F. The exact algorithm changes from AC unit to unit, but you get say 20 mins of heating, and then it will flip to 5 mins of AC while not running the oudoor fan, where an electric (or maybe gas) furance will heat the indoor air after it flows over the indoor coil which is cooling the air. So its a double wammy, its taking 5+ mins of operation back at an even higher wattage. AKA the COP goes negative for 5 minuites... Which will pull the SEER numbers down pretty hard, and that unit actually has pretty poor numbers for being variable speed compressors/etc.(edit: should be SCOP, since SEER(2) is just the ac side, that unit looks to be optimized for heating. Either way, depending on which efficienty spec you pay attention to, the 'problem' tends to be that the SCOP/HSPF/etc numbers are calculated using 'moderate' temp data, so below freezing temps are a minority of the calculation) I poked around a bit looking for the install/service guide for that unit but didn't find one detailing the defrost algorithm.
      - tharkun__ 2y ago
        Not your parent. We had a Fujitsu AOU15RLS3 installed ~10 years ago. 25.3 SEER apparently, EER 13.9. Also r410A. We mainly got it for AC in summer but we'll take the heating of course. Pretty cold winters here. Minimum Outdoor Temperature for Heating: -5°F Yeah that's about as cold as it's right now actually. During the day! We'll definitely use the propane fireplace in winter, especially when the power goes out, which has happened more frequently in recent years, as "proper winter" has given way to more freeze / thaw type stuff with ice storms.
- broken-kebab 2y ago
  Can you elaborate on the statement in the first para? Is it a guess, calculation, or there are real-world data?
  - Tostino 2y ago
    A heat pump can be well over 100% efficient based on the energy input for equivalent resistive / chemical heating. E.g. your heat pump could use 100w of electricity to move 400w worth of heat (if generated resistively) from the outside to inside. There have been multiple studies done that show that current generation heat pumps are quite a bit more efficient for a given volume of gas to burn it in an electrical generation plant and use a heat pump than it is to burn it in the house / building.
    - broken-kebab 2y ago
      I see, but it's still mostly a theory unless we count in all small nuances. Like for a place where winters are really frosty heat-pump usually can't help enough (my own experience), and it seems they come with resistive heating built-in nowadays. Which may change the picture. Also, I'm not a specialist, but my guess is that delivery (or how they call it in the industry) of electricity can be priced in potentially wide range.
      - Tostino 2y ago
        Yup, that was all accounted for in what I read (well over a year ago, can't find the link...sorry). It was also for a northern climate country (possibly the UK, maybe Norway, memory is failing me here), so it was not "best case" for heat pumps. They took into account losses from generation, transmission, number of days so cold that it is acting as close to a resistive heater (100-120% efficiency), etc. It was pretty comprehensive. It was from a "what is the best way to lower our use of fossil fuels" perspective, and acknowledged that switching out all boiler systems for heat pumps would be a high cost, but it wasn't really a study on the economics of it. Just a resource usage perspective.
chippiewill 2y ago
> Here in the UK, natural gas is used to provide electricity[1], so switching to a heat pump right now isn't likely to help with the environment Efficiency of a typical combi boiler is 90%. The notional efficiency of a heat pump in UK climate will be around 300-400% (or rather 3-4 COP). Even accounting for transmission losses etc. a heat pump powered from gas turbines is better for the environment than a combi boiler. And that's assuming the grid doesn't become more green over time. It's not exactly uncommon for cold snaps to be windy too, so it could be 80% renewables. Put it this way, a gas boiler is never going to become more green, a heat pump is going to become more green over it's lifespan (especially in the UK which has very aggressive grid decarbonisation plans).
- SlightlyLeftPad 2y ago
  The incentive structure is broken right now. It costs ~4x to operate a heat pump compared to a gas furnace in California right now. Even with very low use and roof top solar my electric bill is $250 a month when, before heat pump it was $80 with heavier use.
  - scoofy 2y ago
    Yes... that's because we're talking about externalities that an electorate wants to go away, but doesn't want to actually pay for. The entire problem is that we aren't paying the actual cost of what we are consuming, and the cost of a product without these externalities is slightly more, but without making people pay for the externalities, it's not marketable. This is the tragedy of the commons, and it's only a conundrum because the electorate wants to have their cake and eat it too.
    - Spivak 2y ago
      I see this argument a lot that "if only they priced in externalities the numbers would come out in favor of electricity" but I haven't seen a calculation of those externalities that isn't effectively just making up a number. Like I just picked one from a .edu https://scarab.bates.edu/cgi/viewcontent.cgi https://scarab.bates.edu/cgi/viewcontent.cgi and it's just comical with 980% externalities. A number that can be turned into actual policy seems impossible to reach. It seems like the way forward is just make the thing you want people to do cheaper than the status quo, artificially or not, and let people's economic incentive kick in. But if it's artificial you can't do a California and rug pull net metering.
thebruce87m 2y ago
> Here in the UK, natural gas is used to provide electricity[1], so switching to a heat pump right now isn't likely to help with the environment You can view the live production here: https://electricityproduction.uk https://electricityproduction.uk 51% renewables as I write this, and it’s only going to increase over time. I bet the people were arguing about the coal generation until we switched that off. > because gas is vastly cheaper per unit energy https://www.ofgem.gov.uk/energy-price-cap https://www.ofgem.gov.uk/energy-price-cap Looking at the prices, and considering heat pumps are 300-400% efficient per kWh it looks like heat pumps may be slightly more expensive, although on a low night tariff it might be closer or cheaper if you consider 8 hours at 7p/kWh.
- sjducb 2y ago
  Great comment, from a carbon perspective it’s even better than 51% . 16% is nuclear, and 19% is imported from France which is about 60% nuclear. Right now only 10-12% of our electricity is coming from burning gas.
iosguyryan 2y ago
Not to mention the footprint of making something new, disposing the old, and transport.
cjrp 2y ago
> Here in the UK, natural gas is used to provide electricity In the past year, natural gas provided 27.4% of the generated electricity. Wind provided 31.1%. Scroll down on https://grid.iamkate.com https://grid.iamkate.com and choose "Past year" to see the full breakdown.

by rlpb 2y ago

harg 2y ago

You get more heat out of using a given quantity of gas to generate electricity which is used to to power a heat pump than you do by burning the gas directly for heat, even when considering generation and transmission losses etc. Given that even during a time of low output from renewables we still only rely on 53% gas for electricity generation it's still much more beneficial environmentally to use a heat pump. The monetary cost is another story though, and I agree we do need to work on weaning ourselves off gas.

StillBored 2y ago
In areas with moderate outdoor temperatures. Anywhere that the heatpump is going through defrost cycles, that statement is likely false because the COP is likely 1 or less when that starts happening. Then on the generation side, its worse if the NG generation isn't a modern combined cycle plant. which also tends to nix places with a lot of renewable generation because the NG plants are just peaker gas turbines with much lower efficiency than plants designed for continuous use. So, its all situational, but at the same time if one has the choice for cheap NG using that as a second stage and setting the crossover heatpump temperature at the cost/BTU intersection between the heatpump and NG second stage is a rough approximation of the enviromental costs as well as the actual cost.
- triceratops 2y ago
  > In areas with moderate outdoor temperatures. Anywhere that the heatpump is going through defrost cycles, that statement is likely false because the COP is likely 1 or less when that starts happening. Modern heat pumps have a COP close to 2 at 5F/-15C while still delivering 50k+ BTUs. Here's one example: https://ashp.neep.org/#!/product/68628/7/25000/95/7500/0///0 https://ashp.neep.org/#!/product/68628/7/25000/95/7500/0///0
  - StillBored 2y ago
    While heating, That isn't even a particularly efficient unit (EER 9), and not all all unusual for r410 (which is basically banned for new sales in the USA since jan 1st) But it has a 150W pan heater, but I don't think that is its primary defrost mode, at least its not going to be at 50k btu at those temperatures unless its also really dry. The pan heater is probably to just assure that the coil melt water doesn't build up in the base pan. For most of the forced air systemms in the USA, the deforst mode is as I mentioned triggered via outdoor coil temp/runtimes and somewhere below an ambient of ~30F, which will be a coil temp of ~20F. The exact algorithm changes from AC unit to unit, but you get say 20 mins of heating, and then it will flip to 5 mins of AC while not running the oudoor fan, where an electric (or maybe gas) furance will heat the indoor air after it flows over the indoor coil which is cooling the air. So its a double wammy, its taking 5+ mins of operation back at an even higher wattage. AKA the COP goes negative for 5 minuites... Which will pull the SEER numbers down pretty hard, and that unit actually has pretty poor numbers for being variable speed compressors/etc.(edit: should be SCOP, since SEER(2) is just the ac side, that unit looks to be optimized for heating. Either way, depending on which efficienty spec you pay attention to, the 'problem' tends to be that the SCOP/HSPF/etc numbers are calculated using 'moderate' temp data, so below freezing temps are a minority of the calculation) I poked around a bit looking for the install/service guide for that unit but didn't find one detailing the defrost algorithm.
    - tharkun__ 2y ago
      Not your parent. We had a Fujitsu AOU15RLS3 installed ~10 years ago. 25.3 SEER apparently, EER 13.9. Also r410A. We mainly got it for AC in summer but we'll take the heating of course. Pretty cold winters here. Minimum Outdoor Temperature for Heating: -5°F Yeah that's about as cold as it's right now actually. During the day! We'll definitely use the propane fireplace in winter, especially when the power goes out, which has happened more frequently in recent years, as "proper winter" has given way to more freeze / thaw type stuff with ice storms.
broken-kebab 2y ago
Can you elaborate on the statement in the first para? Is it a guess, calculation, or there are real-world data?
- Tostino 2y ago
  A heat pump can be well over 100% efficient based on the energy input for equivalent resistive / chemical heating. E.g. your heat pump could use 100w of electricity to move 400w worth of heat (if generated resistively) from the outside to inside. There have been multiple studies done that show that current generation heat pumps are quite a bit more efficient for a given volume of gas to burn it in an electrical generation plant and use a heat pump than it is to burn it in the house / building.
  - broken-kebab 2y ago
    I see, but it's still mostly a theory unless we count in all small nuances. Like for a place where winters are really frosty heat-pump usually can't help enough (my own experience), and it seems they come with resistive heating built-in nowadays. Which may change the picture. Also, I'm not a specialist, but my guess is that delivery (or how they call it in the industry) of electricity can be priced in potentially wide range.
    - Tostino 2y ago
      Yup, that was all accounted for in what I read (well over a year ago, can't find the link...sorry). It was also for a northern climate country (possibly the UK, maybe Norway, memory is failing me here), so it was not "best case" for heat pumps. They took into account losses from generation, transmission, number of days so cold that it is acting as close to a resistive heater (100-120% efficiency), etc. It was pretty comprehensive. It was from a "what is the best way to lower our use of fossil fuels" perspective, and acknowledged that switching out all boiler systems for heat pumps would be a high cost, but it wasn't really a study on the economics of it. Just a resource usage perspective.

chippiewill 2y ago

> Here in the UK, natural gas is used to provide electricity[1], so switching to a heat pump right now isn't likely to help with the environment Efficiency of a typical combi boiler is 90%. The notional efficiency of a heat pump in UK climate will be around 300-400% (or rather 3-4 COP). Even accounting for transmission losses etc. a heat pump powered from gas turbines is better for the environment than a combi boiler. And that's assuming the grid doesn't become more green over time. It's not exactly uncommon for cold snaps to be windy too, so it could be 80% renewables. Put it this way, a gas boiler is never going to become more green, a heat pump is going to become more green over it's lifespan (especially in the UK which has very aggressive grid decarbonisation plans).

SlightlyLeftPad 2y ago
The incentive structure is broken right now. It costs ~4x to operate a heat pump compared to a gas furnace in California right now. Even with very low use and roof top solar my electric bill is $250 a month when, before heat pump it was $80 with heavier use.
- scoofy 2y ago
  Yes... that's because we're talking about externalities that an electorate wants to go away, but doesn't want to actually pay for. The entire problem is that we aren't paying the actual cost of what we are consuming, and the cost of a product without these externalities is slightly more, but without making people pay for the externalities, it's not marketable. This is the tragedy of the commons, and it's only a conundrum because the electorate wants to have their cake and eat it too.
  - Spivak 2y ago
    I see this argument a lot that "if only they priced in externalities the numbers would come out in favor of electricity" but I haven't seen a calculation of those externalities that isn't effectively just making up a number. Like I just picked one from a .edu https://scarab.bates.edu/cgi/viewcontent.cgi https://scarab.bates.edu/cgi/viewcontent.cgi and it's just comical with 980% externalities. A number that can be turned into actual policy seems impossible to reach. It seems like the way forward is just make the thing you want people to do cheaper than the status quo, artificially or not, and let people's economic incentive kick in. But if it's artificial you can't do a California and rug pull net metering.

thebruce87m 2y ago

> Here in the UK, natural gas is used to provide electricity[1], so switching to a heat pump right now isn't likely to help with the environment You can view the live production here: https://electricityproduction.uk https://electricityproduction.uk 51% renewables as I write this, and it’s only going to increase over time. I bet the people were arguing about the coal generation until we switched that off. > because gas is vastly cheaper per unit energy https://www.ofgem.gov.uk/energy-price-cap https://www.ofgem.gov.uk/energy-price-cap Looking at the prices, and considering heat pumps are 300-400% efficient per kWh it looks like heat pumps may be slightly more expensive, although on a low night tariff it might be closer or cheaper if you consider 8 hours at 7p/kWh.

sjducb 2y ago
Great comment, from a carbon perspective it’s even better than 51% . 16% is nuclear, and 19% is imported from France which is about 60% nuclear. Right now only 10-12% of our electricity is coming from burning gas.

iosguyryan 2y ago

Not to mention the footprint of making something new, disposing the old, and transport.

cjrp 2y ago

> Here in the UK, natural gas is used to provide electricity In the past year, natural gas provided 27.4% of the generated electricity. Wind provided 31.1%. Scroll down on https://grid.iamkate.com https://grid.iamkate.com and choose "Past year" to see the full breakdown.