this post was submitted on 11 Mar 2024
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Yes, heat pumps slash emissions even if powered by a dirty grid | Installing a heat pump now is better for the climate, even on U.S. electricity generated mostly by fossil fuels. Here’s why (www.canarymedia.com)
submitted 8 months ago by [email protected] to c/[email protected]
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The article doesn't go into it, but a key advantage they have is that heat pumps move heat, rather then trying to generate it. So they can move a lot more heat into your house than would be generated by running the electricity they use through a resistor. This makes them effectively more than 100% efficient (the exact amount depends on temperature) as compared with burning a fuel or resistive heat.

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[–] HobbitFoot 16 points 8 months ago (1 children)

Maybe not in the article, but I've heard in other places that a carbon heavy grid still gets enough energy to the heat pump that the heat pump's efficiency can offset that increase.

You're also installing a system that is easier to decarbon in the future, which isn't the case for natural gas.

[–] [email protected] 11 points 8 months ago* (last edited 8 months ago) (1 children)

It is really not hard. Heat pump coefficients of efficiency floor at 1, but typically range between ~2.5 and 7. That is, for every joule of energy they consume, they pump 2.5 to 7 joules of heat into the conditioned space.

So you have to just look at efficiencies involved.

  • The electric heat pump (theoretically ~250-700% efficient at warming a space)
  • The efficiency of energy transmission on the electrical grid (maybe around 90% ish? Depends on a lot of factors)
  • The fossil fuel furnace (theoretically something like 90-100% efficient)
  • The efficiency of the residential fossil fuel delivery system (last I read, something around 5% of natural gas ends up just leaking)
  • The efficiency at conversion of chemical to electrical energy by fossil production plants (and this one is rough -- I see numbers like 40-60% efficient)

Still, we're just summing stuff. And while I won't pretend any napkin math here is the same as a formal research project, we can plainly see that the HUGE energy efficiency of heat pumps can easily eclipse the inefficiency of fossil electrical production, all else being equal. Of course, whether it actually WILL be better than a fossil furnace will depend on local factors, but these places are increasingly becoming edge cases. And then, on top of that, you unlock future potential to seamlessly switch fuel sources from fossils to renewables, which becomes very important in lifecycle cost analysis.

[–] [email protected] 5 points 8 months ago* (last edited 8 months ago) (1 children)

This is the same reason electric cars beats ICE (gas driven) cars even when charged on coal power. Big coal plants and the distribution grid are more efficient than small scale car engines.

You need combustion engines to be BIG to get past 30-40% efficiency ranges, but the really big power plants can just perform efficient burns and heat water to drive efficient turbines, which is impossible in cars. And the rest of losses in electric cars are either minimal or equivalent, so you get a big net benefit.

Even better than that is an electric bus and other public transit!

[–] [email protected] 1 points 8 months ago

Even better when your busses/transit are powered by a pantograph.