I would venture to guess that most residential heating in the world is provided by non-heat pump sources. In many parts of the United States, my understanding

I would venture to guess that most residential heating in the world is provided by non-heat pump sources. In many parts of the United States, my understanding is that it would either be natural gas fired furnaces with forced air, oil fired furnaces (with forced air? not sure), radiators (with water heated by gas or oil fired furnaces), or electric resistive heating elements (e.g. baseboard heaters).