Which of the following is NOT a main type of residential heating?

Solar heating is indeed a method used in some residential settings, but it is not typically categorized as one of the main types of heating systems when discussing standard residential heating solutions. The primary categories usually focus on more traditional methods such as forced air heating, radiant heating, and electric systems. These are systems that are widely adopted and generally recognized in the industry for their conventional applications.

Radiant heating involves systems that heat floors or walls to warm up the space through radiation. Forced air heating uses a system of ducts and vents to distribute heated air throughout a home. Electric systems can include baseboard heaters or electric furnaces that utilize electrical energy to generate heat for living spaces. Each of these main types has established infrastructure and widespread use in residential settings, making them more primary compared to the less conventional solar heating.