What is a British Thermal Unit?

The British Thermal Unit, or Btu, is a standard unit of energy used in the US, Canada, and the UK.  Expressing energy as a BTU allows us to compare the energy content of different fuels.

One Btu is the amount of energy it takes to heat 1 pound of water (1 pint) 1 degree Fahrenheit — which is, approximately, the energy released by burning 1 kitchen match down to your finger.

• One kilowatt hour, which is enough to run a toaster for about an hour, equals 3,412 Btus.
• One cord of wood, which is enough to heat a medium-sized house through the winter, equals 30 million Btus.
• One quad, which is one quadrillion Btus, is about how much energy that biomass, geothermal, solar, and wind sources, combined, feed into American electric plants in one year (and then two-thirds of it is wasted.)

Photo sources: Cornicello, Roger Wendell, Spoon Sisters.