British Thermal Unit - Associated Units

Associated Units

The Btu per hour (Btu/h) is the unit of power most commonly associated with the Btu. The term is sometimes shortened to Btu hour (Btu.h) but both have the same meaning.

• 1 watt is approximately 3.41214 Btu/h
• 1000 Btu/h is approximately 293.071 W
• 1 horsepower is approximately 2,544 Btu/h
• 1 "ton of cooling," a common unit in North American refrigeration and air conditioning applications, is 12,000 Btu/h. It is the amount of power needed to freeze one short ton of ice in 24 hours, and is approximately 3.51 kW.
• 1 therm is defined in the United States and European Union as 100,000 Btu—but the U.S. uses the Btu_{59 °F} whilst the EU uses the Btu_IT.
• 1 quad (energy) (short for quadrillion Btu) is defined as 1015 Btu, which is about one exajoule (1.055 × 1018 J). Quads are used in the United States for representing the annual energy consumption of large economies: for example, the U.S. economy used 99.75 quads in 2005. One quad/year is about 33.43 gigawatts.

The Btu should not be confused with the Board of Trade Unit (B.O.T.U.), which is a much larger quantity of energy (1 kW·h, or about 3412 Btu).

The Btu is often used to express the conversion-efficiency of heat into electrical energy in power plants. Figures are quoted in terms of the quantity of heat in Btu required to generate 1 kW·h of electrical energy. A typical coal-fired power plant works at 10,500 Btu/kW·h, an efficiency of 32–33%.