Why are the “efficiencies” of heating appliances different? Why don I just use the differences in fuel costs to make comparisons?
When comparing operating costs of heating appliances, it is important to make adjustments for their differences in ‘operating efficiency.’ If a space heater is 70% efficient, it means that 70% of your purchased fuel or electricity is actually being converted into space heat. The other 30% provides the energy that is needed in the process of burning the fuel or converting electricity into space heat. In water heaters, 90% efficiency would mean that 90% of the heat is actually being applied to the water; the other 10% would be “lost” through the walls of the water heater.
