[dcuthbertson]

I'm curious as to how low a temperature your heat pump will operate. I live in New England and replaced a whole-house air conditioner with a heat pump, but the heat pump works only to 35F. Much colder than that, and an auxiliary electric heater kicked in. The first Winter cost me about $800 over my gas-fired forced hot water heating system. I had the contractor disable the electric heat in the Spring and rewire the thermostats to start the (high efficiency) furnace when the outdoor temp got too low.

[apexalpha]

Mine can go until -25c they say: https://www.nibe.eu/en-eu/products/heat-pumps/air-water-heat...

We don't ever get those temps so I should be fine.

My biggest issue is not cold but mist. I live near a river in a valley and have underestimated how much mist hurts performance around ~1c outside.

It needs to defrost often, because of the high moisture content in the outside air where I live.

But it also has a normal, resistive heating 9kW backup. But for financial reasons this is considered 'emergency only'.

[zihotki]

Keep in mind that heat pumps have a limit how much they can pump (it also depends on temp., there is less heat in 35F air). If your house is not well insulated, at a lower temperature it would be loosing more energy and eventually it would reach the threshold where it's performance is not enough to keep up.

[testing22321]

We got a heat pump in BC Canada, it’s rated down to -30C.

We also got solar, our entire power bill (all heating, cooking, lights, computers, etc) is $500 for the year. Best decision ever.

[anotherhue]

That depends on the refrigerant, the new Mitsubishis are effective at that and lower temperatures.