Unit or Prefix DescriptionBtu (British
Thermal Unit)
Btu is a unit of energy used in the United States.
In most countries it has been replaced with the
joule. A Btu is the amount of heat required to
raise the temperature of 1 pound of water by 1°F.
1 watt is approximately 3.4 Btu/hr. 1 horsepower
is approximately 2,540 Btu/hr. 12,000 Btu/hr. is
referred to as a “ton” in many air-conditioning
applications.Horsepower Primarily used in the automobile industry. 1
horsepower (HP) is equivalent to 746 watts.
Kilo- 1,000 or 10^3 . 1 kW = 10^3 watts.
Mega- (M) 1,000,000 or 10^6 . 1 MW = 10^6 watts.
Kilowatt hour
(kWh)
Unit of energy equal to 1,000 watt hours or 3.6
megajoules. The kilowatt hour is most
commonly known as a billing unit for energy
delivered to consumers by electric utilities. The
kilowatt (kW) is a unit of power, a measure of
energy used at a given moment, not over time
(e.g., a car is traveling at a speed of 60 miles per
hour), whereas the kilowatt hour (kWh) is a unit
of total energy used over a specific period of
time (e.g., a car used a gallon of gasoline to go
13 miles in 30 minutes). Examples: A heater
rated at 1,000 watts (1 kilowatt), operating for
one hour uses one kilowatt hour (equivalent to
3.6 megajoules) of energy. Using a 60 watt
lightbulb for one hour consumes 0.06 kilowatt
hours of electricity.