Energy Concepts and Terms

This page includes a quick orientation to common energy concepts and terms.

Energy and Power

Power = Energy/Time

  • Power is Energy per unit time.
  • Energy is related to power as gallons are related to gallons per minute.
  • British Thermal Unit (Btu) - A Btu is the amount of energy required to raise the temperature of one pound of water 1 degree Fahrenheit.
  • Therm = 100,000 Btu, heat energy sources such as natural gas and steam may be sold in therms.
  • Kilowatt (kW) – A measure of power equal to 1,000 watts. Also equal to 3,412 Btu/hr.
  • Kilowatt-hour (kWh) - A kilowatt-hour is the quantity of energy delivered when power flows at the rate of one kilowatt for one hour. It is equal to 3,412 Btu.
  • Cooling Ton - A cooling ton is 12,000 Btu/hr. It is the rate of cooling required to produce one ton of ice in a 24 hour period. The capacity of most air conditioning systems are expressed in tons.

How Much Energy is In?...

Energy Source Energy Content (Btu) Units
Sunlight 200 Btu per hour per square foot
Wind 75 Btu per hour per square foot of wind turbine swept area in 22 mile per hour wind.
Biomass 7,000 Btu per pound (value is for switchgrass)
Wood 8,000-10,000 Btu per pound
Coal (Anthracite) 14,000-15,000 Btu per pound
Coal (Bituminous) 10,500-14,000 Btu per pound
Oil (#2 Fuel) 137,000-141,800 Btu per gallon
Natural Gas 950-1,150 Btu per cubic foot
Gasoline 109,000-125,000 Btu per gallon
Kerosene 130,000-140,000 Btu per gallon
Nuclear Fuel (Uranium) 35,000,000,000 Btu per pound Uranium-235