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Comment by seniorsassycat | Hacker News Reader

A heat pump in a −273 °C space will convert electricity to heat at a 1:1 ratio.

If you count the heat taken from the space around the condenser, which you should based on Google's definition, heat pumps are only 100% efficient.

Calling heat pumps >100% efficient is like calling my solar water heater >100% efficient. True if you only count the electrical input, and not other sources of energy.

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You will be pleased to know that the majority of heat pumps are installed in homes whose exteriors stay above 0 kelvin year round. Also, in what I assume is an efficiency feature, most heat pumps do not allow operation in a zero Kelvin environment.

Also, to nit pick: Kelvins are not degrees and do not use a ° sign.

Damn, I've been looking for a zero Kelvin heat pump that works in a vacuum to heat my spherical cows.

Maybe you wouldn't need to heat them so much if they weren't frictionless.

Gotta watch out for that Maxwell brand heat pump.

Are you trying to liquify vacuum? It's challenging. Try to use a heat pump based on the Casemir effect, fluctuating virtual particles violate the energy conservation of the system for short periods.

And, as a bonus efficiency feature, most heat pumps are installed with the condenser external to the home!

Yes, if you draw an imaginary box around the home and the outdoor/underground condenser, they're exactly 100% efficient, but if you only consider the inside of the home and ignore that the condenser is taking in heat energy from the outside, they're more than 100% efficient.

The power station and natural gas plants are outside my house too, so my restive floor heaters and furnace are >100% efficient.

Just draw an imaginary line around my pocket book then. I pay for the energy I'm getting from the power station. Beyond capex, I don't pay for the energy I'm getting from the heat exchanger.

Anecdotally, I have come across hotel bar fridges running in entirely enclosed cupboards. Even the power cord exited the box with a rubber seal.

Nice attention to detail in physical craftmanship though!

did not realize kelvin is not a degree. I fixed my comment.

Good thing they wrote −273 °C and not "0 °K".

Pretty sure they edited it.

I was under the impression that HN indicated when a comment was edited. Maybe not and I got mixed up with elsewhere.

Edit: Apparently I'm completely wrong. Carry on and I'll eat my downvotes with aplomb.

This is incorrect. We measure the "efficiency" of a heat pump by the amount of heat moved into a space divided by the work energy provided to the pump (electricity in this case). This is called the "coefficient of performance". Typical heat pumps have a CoP of 3 or more. Meaning, you can spend 100W of electricity to pump 300W of heat into your home. A purely resistive heater only has a CoP of 1.

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