Why are gas boilers more energy efficient overall than electric fires?
In the case of a gas boiler, the gas is burned on-site. Depending on the design of the gas boiler, around 60% to 85% of the heat from combustion is used for heating the room. So the fuel used is (room heat demand) ÷ (boiler efficiency). In the case of an electric heater, the electricity is produced at a central generating plant. Some of these are powered by nuclear fuel, some by renewable resources such as hydro, wind or sun, but most of them burn fuel (gas, or oil, or coal) to create heat that is then turned into electricity. The laws of thermodynamics set a limit as to how efficient this conversion can be, and generally well under 50% of the heat from combustion can be turned into electricity. Also a substantial fraction of the power that is generated is lost in the process of transmission from the power plant to the home. Therefore the fuel used is (room heat demand) ÷ (conversion efficiency x transmission efficiency.) Since the denominator in the second case is usually smaller than
