Coal supply and consumption are usually expressed in units of metric tons (tonnes); 1 metric ton is equal to about 2205 pounds. A typical coal-fired power plant consumes about 2 million tonnes of coal per year, and annual coal consumption in the United States is about 1 billion tonnes per year. Coal prices are expressed in units of dollars per gigajoule ($/GJ). A tonne of coal contains about 23.5 GJ of energy.

Petroleum and gasoline supply and consumption are expressed in units of barrels (bbl); a barrel contains 42 U.S. gallons or 159 liters. Units of barrels of gasoline equivalent (bbl gasoline eq) represent the energy content of other liquid fuels (e.g., ethanol) in terms of the energy content of a barrel of motor gasoline. The United States consumes about 9 million barrels of motor gasoline per day and over 7 billion barrels of liquid fuels (crude oil, finished products, and other liquid fuels) per year.

Natural gas supply and consumption are expressed in units of trillion cubic feet (Tcf). The United States consumes about 23 Tcf of natural gas each year.

Biomass supply for liquid fuels production is expressed in units of dry tonnes; 1 dry tonne is equal to about 2205 pounds. The dry ton equivalent is 2000 pounds.

Total energy supply and consumption are expressed in British thermal units (Btu) and quads (quadrillion Btu = 10¹⁵ Btu). A Btu is defined as the amount of energy (in the form of heat) needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit. The energy content of electricity and natural gas, liquid, and coal fuels can be quantified in terms of Btu using the following approximate factors: