How Can a Heat Pump Get Heat from −10 °C (14 °F) Air?

Your heat pump can put three to four times more heat into your home than the electricity it uses, on a mild day. That sounds like cheating. It isn't. In this deep dive, we take it slowly: what heat really is, the squeeze-and-expand trick that carries heat uphill, why your air conditioner is the same machine running backwards, how a heat pump finds heat in air at −10 °C (14 °F), and an honest look at whether it's worth it. 0:00 A machine that seems to break physics 0:47 Heat is movement 2:10 The trick: squeeze and expand 4:47 Your AC, but backwards 5:35 How can it get heat from −10 °C (14 °F) air? 7:53 Is it worth it? 9:29 What should the next deep dive be? Numbers are typical values, not guarantees. Real performance depends on the unit, the house, the installation and the weather. SOURCES UK real-home study, COP 3.4 at 10 °C (50 °F), yearly average 2.93 over 428 air source heat pumps, flow temperatures (DESNZ / Energy Systems Catapult, Electrification of Heat): https://esc-production-2021.s3.eu-wes... US cold-climate field study, COP 3.5 mild to 1.8 at −26 °C (−15 °F), electric heater COP 1 (ACEEE 2024): https://www.aceee.org/sites/default/f... US DOE cold-climate heat pump field data (PNNL-37127): https://www.pnnl.gov/main/publication... R32 boiling point (NIST Chemistry WebBook): https://webbook.nist.gov/cgi/cbook.cg... R290 (propane) boiling point (NIST Chemistry WebBook): https://webbook.nist.gov/cgi/cbook.cg... Absolute zero and water's boiling point (NIST): https://www.nist.gov/pml/owm/si-units... Operating down to −25 °C (−13 °F) (Daikin Altherma 3 R): https://www.daikin-ce.com/en_us/produ... Operating down to −28 °C (−18 °F) (Daikin Altherma 3 H HT): https://www.daikin.eu/en_us/product-g... Boiler flow temperatures of 70–80 °C (158–176 °F) (Nesta): https://www.nesta.org.uk/report/the-i... Noise, about 45 dB(A) at 3 m, like a fridge (alpha innotec): https://www.alpha-innotec.com/en/prod... Noise levels (Hive): https://www.hivehome.com/blog/air-sou... Defrost cycle (Trane): https://www.trane.com/residential/en/... Defrost cycle (Lennox): https://www.lennox.com/residential/le... Typical heat pump efficiency (EDF): https://www.edfenergy.com/heating/ele... Heat pump basics: https://en.wikipedia.org/wiki/Heat_pump Compression heating and expansion cooling: https://en.wikipedia.org/wiki/Adiabat...