See central air.
A heat pump is just like a central air-conditioner when running in COOL mode. However, during the winter months or when it is cold outside, a heat pump has a component called a reversing valve that allows it to reverse the flow of
refrigerant. Instead of removing the heat and humidity from the structure and subsequently cooling it as a result, a heat pump extracts ambient heat from the outside air and moves it into the structure. There is heat in the air right down to
absolute zero. However, once it gets below freezing,
even the newest, most efficient, top-of-the-line heat pumps tend to struggle in terms of heating
performance without some sort of backup heat.
In areas where it is
almost always warm, like many parts of Florida, a heat pump with no backup heat (gas, oil, electric) is just fine. However, the farther North you go, the more likely you are to need backup heat. Electric strip heat is little more than oversized toaster coils with a fan
that blows over them to circulate the heat through the building's ductwork. This will work anywhere in the country, but the farther North you go, the more expensive it is going to be to run it. In parts of the country with really cold winter climates, a heat pump matched up with a gas or oil furnace, or even a hot water boiler, is a very efficient choice, possibly even more efficient than a straight-cool central air-conditioner matched up with a furnace. This is called a hybrid or dual-fuel system.
Those new tract homes in Florida have those
efficient heat pumps instead of regular electric heat.
My friend's house in the
Pennsylvania has a heat pump, and it sucks at heating when it gets below forty degrees!
My new house has a heat pump and a gas furnace for maximum
efficiency