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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.
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).
The watt, kilogram, joule, and the second are part of the International System of Units (SI). The hour is not, though it is accepted for use with the SI.Since a watt equals one joule per second and because one hour equals 3600 seconds, one watt-hour per kilogram can be expressed in SI units as 3600 joules per kilogram.
The fuel consumption is an equivalent measure for cars sold outside the United States, typically measured in litres per 100 km traveled; in general, the fuel consumption and miles per gallon would be reciprocals with appropriate conversion factors, but because different countries use different driving cycles to measure fuel consumption, fuel ...
Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time. For example, when a light bulb with a power rating of 100 W is turned on for one hour, the energy used is 100 watt hours (W·h), 0.1 kilowatt hour, or 360 kJ. This same amount of energy would light a 40 ...
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/kWh (3.1 kWh/kWh), an efficiency of 32–33%. [25]
The dimension of power is energy divided by time. In the International System of Units (SI), the unit of power is the watt (W), which is equal to one joule per second. Other common and traditional measures are horsepower (hp), comparing to the power of a horse; one mechanical horsepower equals about 745.7 watts.
Example: For a heat pump delivering 120,000,000 BTU during the season, when consuming 15,000 kWh, the HSPF can be calculated as : HSPF = 120000000 (BTU) / (1000) / 15000 (kWh) HSPF = 8. The HSPF is related to the non-dimensional Coefficient of Performance (COP) for a heat pump, which measures the ratio of heat delivered to work done by the ...