Cold weather, told straight

A heat pump pulls warmth out of cold air. The sentence sounds wrong on first read and less wrong the longer you look at it. Cold air has heat in it. Air at minus ten has heat in it. Air at minus thirty has heat in it. The machine just needs to be built to find it.

The good ones now are.

What the numbers say

The current generation of cold-climate heat pumps holds usable output down to roughly minus fifteen Fahrenheit, which is minus twenty-six Celsius. Below that, output tapers, and most homes pair the heat pump with a small backup, often electric resistance, occasionally a furnace kept around for the worst week of the year. The backup runs maybe three to five percent of the heating hours. The heat pump handles the other ninety-five.

About ninety-four percent of Americans, by USDA cold-zone classification, live in places where a modern heat pump can be the primary heat source year-round.

Why the old reputation lingers

For a long time, heat pumps were specified into the wrong climates by the wrong installers using the wrong sizing. The machines themselves were less capable, and the people installing them were less informed. Both of those things have changed. The reputation will catch up. We are trying to help it catch up.

The cold-climate models you want to ask about by name belong to the lines that the engineers actually compete on. Mitsubishi calls theirs Hyper-Heat. Daikin calls theirs Aurora. LG has a competitive cold-climate line. There are others, and the list grows yearly. The thing to look for on the spec sheet is rated capacity at five degrees Fahrenheit, not just the cooling capacity at ninety-five. Any sales person who does not know what that means is not the sales person to buy from.

Two things to make sure of

The first is your house, not the heat pump. A drafty, uninsulated house is hard to heat with anything. Air sealing and insulation are worth doing before, or alongside, the heat pump install. The improvements are typically cheaper than the install, they make the install smaller, and they pay for themselves in comfort even if you change nothing else.

The second is the contractor. Ask which cold-climate models they spec, ask for performance data at design temperature, and ask how they plan to size the system. A good answer to those three questions is the strongest predictor of whether the install will perform. A contractor who shrugs and quotes whichever unit happens to be on the truck is a contractor who is going to undersize the system, or oversize it, and either way you will be living with the consequences for fifteen years.

A note for the truly cold. In northern Maine, the upper Midwest, the Canadian Prairies, and most of Alaska, the heat pump is doing real work. The math still pencils out, but the install is harder to get right and the contractor matters more. Be patient with the bid process. Get two quotes minimum. Read reading the quote first.

Cold weather is no longer the heat pump’s problem. It is, mostly, ours.