In the international system, the basic unit of measurement for power is the watt. Watts are the standard unit of measurement for determining the power output of various appliances and for determining overall energy usage. The kilowatt hour, which is equivalent to one thousand watts per hour, is the unit that is most commonly used; however, the watt hour, also known as the consumption of an appliance per hour of operation.
BTU stands for the British Thermal Unit
The amount of heat necessary to increase the temperature of 454 grammes of water from 60 to 61 degrees Fahrenheit is the quantity that is used to define a British Thermal Unit (BTU). Both the cooling power of air conditioning systems and the heating power of fuel are typically defined using the unit of measure known as British Thermal Units per hour (BTU/h).
The power P expressed in watts (W) is equivalent to 3.412141633 times the power P expressed in British thermal units per hour (BTU/hr):
BTU/hr = 3.412141633 × W
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