4 ms·

That can't be right. Heat pumps are commonly 2.5x-4x more efficient than direct heating. "The U.S. Energy Information Administration (EIA) estimates that annua

That can't be right. Heat pumps are commonly 2.5x-4x more efficient than direct heating. "The U.S. Energy Information Administration (EIA) estimates that annual electricity transmission and distribution (T&D) losses averaged about 5% of the electricity transmitted and distributed in the United States in 2017 through 2021." https://www.eia.gov/tools/faqs/faq.php?id=105&t=3 https://www.eia.gov/tools/faqs/faq.php?id=105&t=3

sokoloff 4y ago
The combustion efficiency of the fossil fuel electric generation must also be considered. If that’s 40% efficient, a heat pump with a CoP of 2.5 is very close to a 95% AFUE gas-burning unit.
- pornel 4y ago
  Combined cycle gas power plants are about 60% efficient. Coal power plants are around 40%, but even the dirtiest parts of Florida aren't all coal (https://app.electricitymaps.com/map https://app.electricitymaps.com/map) But of course this is short-sighted, because the grid is greener in most places, and will get even greener over the lifetime of the heat pump, while the gas furnace won't get any better.
nkurz 4y ago
I downvoted you for your overconfidence. Your conclusion might be right, but it's not as straightforward as you suggest. You're right that the transmission losses aren't large, but you seem to be missing the much bigger losses involved in generating electricity from coal. Currently, the average coal fired plant produces electricity at 33% efficiency: https://www.energy.gov/fecm/transformative-power-systems https://www.energy.gov/fecm/transformative-power-systems. That's average, so there are probably plants out there producing at 30%. If we assume another 5% loss for transmission, this takes us down to 25% efficiency as delivered to the consumer. If a heat pump is 3x the efficiency of resistance electric heat, but you are burning 4x the coal to generate the electricity, are you still certain that a 95% natural gas furnace is never the better choice for efficiency? I'm not. I think the heat pump is probably more efficient in many cases, but I wouldn't eliminate the possibility that there are cases where the natural gas wins.
- markus92 4y ago
  This is definitely the the worst case, but in how many places is coal the only thing on the grid? If I look a bit randomly at electricity maps there's barely any place left where it's just coal on the grid.
- jandrese 4y ago
  The problem is in the future when you decarbonize how are you going to do it with a gas furnace? Bio-gas is extremely niche and shows no sign of picking up anytime soon. Meanwhile your local power plant already switched from coal to natural gas, but in the future the grid is going towards wind, solar, and battery storage. You can even install solar panels locally to cut down on transmission losses.
  - ncphil 4y ago
    As someone who has owned or rented homes heated with oil, gas and heat pumps (the latter two in the SE US), my experience has been that the gas and heat pump systems cost about the same same to operate. But when the gas system in our current house had to be replaced about 5 years ago, I went the path of least resistence and got the recommended gas unit. I really regret that decision now, especially given the small difference in installed price. Same with the tankless water heater (although there, gas was all that was available on short notice). The momentum in favor of gas is still enormous, and at least around here strongly influences what installers recommend. Maybe better educated consumers will change that. Unfortunately, I'm going to be stuck with gas into the next decade, with the only consolation being that at least I'm done with oil (the last two oil burners I ran were from the 50s, for steam heat, and cost a fortune to run: one winter in the early 00s about $600 a month).
- dandandan 4y ago
  Why the focus on coal? California as a whole only sourced 3% of its energy from coal in 2021, and some regions were at 0%. It only made up 20% of the entire US' consumption in 2022 https://www.eia.gov/tools/faqs/faq.php?id=427&t=3 https://www.eia.gov/tools/faqs/faq.php?id=427&t=3

sokoloff 4y ago

The combustion efficiency of the fossil fuel electric generation must also be considered. If that’s 40% efficient, a heat pump with a CoP of 2.5 is very close to a 95% AFUE gas-burning unit.

pornel 4y ago
Combined cycle gas power plants are about 60% efficient. Coal power plants are around 40%, but even the dirtiest parts of Florida aren't all coal (https://app.electricitymaps.com/map https://app.electricitymaps.com/map) But of course this is short-sighted, because the grid is greener in most places, and will get even greener over the lifetime of the heat pump, while the gas furnace won't get any better.

nkurz 4y ago

I downvoted you for your overconfidence. Your conclusion might be right, but it's not as straightforward as you suggest. You're right that the transmission losses aren't large, but you seem to be missing the much bigger losses involved in generating electricity from coal. Currently, the average coal fired plant produces electricity at 33% efficiency: https://www.energy.gov/fecm/transformative-power-systems https://www.energy.gov/fecm/transformative-power-systems. That's average, so there are probably plants out there producing at 30%. If we assume another 5% loss for transmission, this takes us down to 25% efficiency as delivered to the consumer. If a heat pump is 3x the efficiency of resistance electric heat, but you are burning 4x the coal to generate the electricity, are you still certain that a 95% natural gas furnace is never the better choice for efficiency? I'm not. I think the heat pump is probably more efficient in many cases, but I wouldn't eliminate the possibility that there are cases where the natural gas wins.

markus92 4y ago
This is definitely the the worst case, but in how many places is coal the only thing on the grid? If I look a bit randomly at electricity maps there's barely any place left where it's just coal on the grid.
jandrese 4y ago
The problem is in the future when you decarbonize how are you going to do it with a gas furnace? Bio-gas is extremely niche and shows no sign of picking up anytime soon. Meanwhile your local power plant already switched from coal to natural gas, but in the future the grid is going towards wind, solar, and battery storage. You can even install solar panels locally to cut down on transmission losses.
- ncphil 4y ago
  As someone who has owned or rented homes heated with oil, gas and heat pumps (the latter two in the SE US), my experience has been that the gas and heat pump systems cost about the same same to operate. But when the gas system in our current house had to be replaced about 5 years ago, I went the path of least resistence and got the recommended gas unit. I really regret that decision now, especially given the small difference in installed price. Same with the tankless water heater (although there, gas was all that was available on short notice). The momentum in favor of gas is still enormous, and at least around here strongly influences what installers recommend. Maybe better educated consumers will change that. Unfortunately, I'm going to be stuck with gas into the next decade, with the only consolation being that at least I'm done with oil (the last two oil burners I ran were from the 50s, for steam heat, and cost a fortune to run: one winter in the early 00s about $600 a month).
dandandan 4y ago
Why the focus on coal? California as a whole only sourced 3% of its energy from coal in 2021, and some regions were at 0%. It only made up 20% of the entire US' consumption in 2022 https://www.eia.gov/tools/faqs/faq.php?id=427&t=3 https://www.eia.gov/tools/faqs/faq.php?id=427&t=3