Common joke says that heaters are 100% effient because all they make is heat. How much energy is actually lost?

Question

Common joke says that heaters are 100% effient because all they make is heat. How much energy is actually lost?

In: Physics

Answer 1

In the context of heating a building, a system is less than 100% efficient if any of the heat generated is lost to the outside world without contributing to the heating of the building. Examples of this would be heated combustion gases going up a chimney or out of a flue. (It doesn’t matter how well the building is insulated; heat lost this way never contributes to the heating of the building, so these losses can be expressed as the efficiency of the heating system.)

Direct electrical heating systems generally don’t lose heat to the outside world this way, so their efficiency in this context can be considered to be 100%.