- Conversion of input energy to thermal energy. Fuel-based or electric resistance heating are both less efficient than heat pumps. The later can deliver several times the heat energy as is used to move it from elsewhere (outside air, the ground).
- Any emissive losses. The electric + brick heat systems seem to be similar to a masonry stove or similar design. If the bricks are on an interior wall, any heat leakage should be into the living space. If on an exterior wall, it's quite possible that much of the heat is radiated to the exterior. Even where placement is central, a wall may leak heat vertically and through the ceiling to the outside.
- Cost of fuels. The electric + brick design would seem to rely on cheaper off-peak electric rates. A more efficient system which more closely follows other electric loads (and hence, uses more high-cost electricity) could cost more whilst utilising fewer kWh of actual electrical energy, for example. Similarly, heat pumps with fallback to electric resistance heat might see similar high-cost patterns during extremely cold weather.
> How can a heating system be inefficient? Does it generate too much waste heat?
Yeah, they do:
1) Heat that's present when people aren't is unnecessary heat.
2) Heat that leaks out of the building is wasted heat.
So isolate the building better...? Yes, of course... But you can never isolate 100%. And heat that's present while people aren't -- see 1) above -- is heat that can (and, to some extent, will!) leak out before ever warming anyone.
