One somewhat simple way to evaluate heating options is to compare the cost of the fuel. To do that, you have to know the energy content of the fuel and the efficiency by which it is converted to useful heat.

Fuels are measured in physical units, such as gallons of oil or propane, cubic feet of natural gas, or kilowatt hours of electricity (kWh). They are also measured by heat content. In the United States, the most commonly used value for expressing the energy value or heat content of a fuel is the British thermal unit (Btu). One Btu is the amount of energy needed to raise the temperature of one pound of water 1°F, when water is at about 39°F. One "therm" is 100,000 Btu.

The chart below provides a list of typical heating fuels and the Btu
content in the units that they are typically sold in the United States.