Study it a bit while it's still warm and look up your local weather. [1] The COP gets worse as Delta(T) increases and heat pumps are nowhere near the theoretic

Study it a bit while it's still warm and look up your local weather. [1] The COP gets worse as Delta(T) increases and heat pumps are nowhere near the theoretical best, so at a certain point it's better to use gas. But that's typically below 0F (-10C). I put in a four way Mitsubishi (2x as expensive but super silent) in my old home. Relatively happy with it, except I don't think the installers put enough coolant in it (it's best to instal a heat pump on a cool day). The air does gets a bit dry, so consider getting a heating humidifier for the night. Finally, if you can afford it and if you can install it, a heat-pump with buried coolant lines really multiplies the efficiency (since the ground is above freezing and acts as a heat store through the seasons) EDIT: [1] If you live near a large body of water, especially if it's salty, it's very unlikely your cold days are cold enough to be a problem for the AC. Unless you live in Thunder Bay. [2] AC is not a huge climate problem. Heating, cars, global supply chains, agriculture are bigger problems. AC just gets the attention because it's considered frivolous. A bigger problem is that modern homes are built with no consideration for cooling. My old house was 100 years old and naturally kept cool. My new house has at least 7 seven!!! skylights. It's impossible to cool. At least 5 of them face north :S