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The Btu should not be confused with the Board of Trade Unit (BTU), an obsolete UK synonym for kilowatt hour (1 kW⋅h or 3,412 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.
kilowatt-hour; Board of Trade Unit: kW⋅h; B.O.T.U. ≡ 1 kW × 1 h ... BTU (International Table) per hour: BTU IT /h ≡ 1 BTU IT /h ≈ 0.293 071 W:
The therm (symbol, thm) is a non-SI unit of heat energy equal to 100,000 British thermal units (BTU), [1] and approximately 105 megajoules, 29.3 kilowatt-hours, 25,200 kilocalories and 25.2 thermies. One therm is the energy content of approximately 100 cubic feet (2.83 cubic metres) of natural gas at standard temperature and pressure. However ...
assumes the 59 °F Btu and the "long scale" quadrillion (10 15) 1.0 ... an obsolete UK synonym for kilowatt-hour 1.0 ...
An air-conditioning unit rated at 72,000 BTU/h (21 kW) (6 tons), with a SEER rating of 10, operates 1000 hours per year at an electric energy cost of $0.12 per kilowatt-hour (kW·h). What is the annual cost of the electric energy it uses?
The notation kW/h for the kilowatt-hour is incorrect, as it denotes kilowatt per hour. The hour is a unit of time listed among the non-SI units accepted by the International Bureau of Weights and Measures for use with the SI. [6] An electric heater consuming 1,000 watts (1 kilowatt) operating for one hour uses one kilowatt-hour of energy.
= [kW⋅h] As total energy consumption is in kilowatt hours and heating degree days are [no. days×degrees] we must convert watts per kelvin into kilowatt hours per degree per day by dividing by 1000 (to convert watts to kilowatts), and multiplying by 24 hours in a day (1 kW = 1 kW⋅h/h).
A heat rate value of 2 kWh/kWh gives an efficiency factor of 50%. A heat rate value of 4 MJ/MJ gives an efficiency factor of 25%. For other units, make sure to use a corresponding conversion factor for the units. For example, if using Btu/kWh, use a conversion factor of 3,412 Btu per kWh to calculate the efficiency factor.