Comment by nkurz | Hacker News Reader

Comment by nkurz | Hacker News Reader

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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. 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.

Sorry to have been unclear - my comment was a response to this specific claim, which only considers power generation via natural gas, not the grid as a whole, nor coal:

"Due to transmission losses, it is cheaper, efficient, and greener to combust natural gas for warmth directly than to burn it at a power plant, feed the power into the grid, and use grid power to run a heat pump."

This statement does leave itself some wiggle room with "cheaper", but in terms of "efficient" it cannot really be true, because the average efficiency of a natural gas power plant is 45% - and if I'm reading this document correctly, that figure already factors in transmission loss:

https://www.eia.gov/todayinenergy/detail.php?id=44436

Good points, but in case anyone is still reading, I feel compelled to stick to my guns: I think it matters where you are. Figures 7 and 8 in this 2022 paper from Lawrence Berkeley Lab give maps of the seasonal minimum heat pump COPs necessary to achieve cost and CO2e equivalence with a 95% efficiency gas furnace: https://escholarship.org/content/qt8pt9155c/qt8pt9155c.pdf.

It requires making some assumptions about heating season air temperatures, but I think it shows that with current electricity generation there are several states where air source heat pumps are actually worse for emissions. And that at current energy prices, there are several states (not necessarily the same) where they are not a win for running costs. Betting on the future "greening of the grid" is a good argument, but the timescale matters. I like the future of heatpumps, but I worry about a backlash if the benefits are oversold.

I appreciate your attention to accuracy in this discussion. I think we are basically arguing against different oversimplifications, not really disagreeing about anything fundamental.

My own house was built with hydronic floor heating, via natural gas. We added a ductless heat pump a few years ago, but we primarily use it for cooling. It would be a clear win from an environmental perspective, since our utility is 80% hydro and 0% coal/oil/gas; but the radiant floors are so much more comfortable that we haven't made much use of electric heating yet. We'll probably have the heat pump upgraded in a year or two, to cover more of the house; perhaps that'll be a good moment to shift our habits and see how it works out.

They aren't real common, but there do exist air-to-water heat pumps that can be used for radiant floors. They usually aren't hot enough for pre-existing baseboard, but hydronic flooring runs cooler. Not sure about availability, but here are some specs from a Canadian manufacturer: https://www.arcticheatpumps.com/specifications.html.

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

I used coal because the GP said they were in an area where coal and natural gas were primarily used for generation. Since coal is used as part of the blend, it seemed reasonable to consider it as a worst case scenario for efficiency. I wasn't objecting to the general conclusion, just the implication that there was clearly no case where natural gas heat might beat a heat pump.

I'd happily concede that in all locations in California a heat pump will be more efficient when averaged over the entire year. I'm less sure about Winnipeg or Whitehorse, especially if we are looking at shorter timescales. Did jmchphers indicate somewhere that he was in California, or even the US? If he's somewhere very cold, I think we still need to at least run the numbers.

(I should probably also add that I've got a heat pump hot water heater and heat pump dryer. I'm a big fan of the technology---I just don't think it's always the head-and-shoulders winner for all people in all locations at all times.)

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.

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).

Power is like real estate. Location. Location. Location. Where I live all/most electricity is generated from hydroelectric. I feel like everyone commenting should post where they live or how their electricity is generated.

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.

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