They certainly don't produce electricity, but they do produce energy. You put in 1 kW of electricity, though, and you might get 5 kW of heat added to your house

They certainly don't produce electricity, but they do produce energy. You put in 1 kW of electricity, though, and you might get 5 kW of heat added to your house. So in a sense, it is producing energy. Now, that energy is coming from somewhere else (in this case, the heat of the ground beneath the house or the air outside), but that's true of electrical generators as well.