## Energy Units

**Energy** is generally defined as the potential to do work or produce heat. This definition causes the SI unit for energy is the same as the unit of work – the** joule (J)**. Joule is a derived unit of energy and it is named in honor of **James Prescott Joule** and his experiments on the mechanical equivalent of heat. In more fundamental terms, 1 joule is equal to:

**1 J = 1 kg.m ^{2}/s^{2}**

Since energy is a fundamental physical quantity and it is used in various physical and engineering branches, there are many **energy units** in physics and engineering.

## Kilowatt-hour (unit: kWh)

**Kilowatt-hour (unit: kWh)**. Kilowatt-hour is a derived unit of energy. It is used to measure energy, especially electrical energy in commercial applications. One kilowatt-hour is equal to one kilowatt of power produced or consumed over a period of one hour (kilowatts multiplied by the time in hours). The kilowatt hour is commonly used by electric utilities as a billing unit for energy delivered to consumers. 1kW . h = 1kW . 3600s = 3600kWs = 3600kJ = 3600000J. One kilowatt-hour corresponds to the heat required to evaporate of 1.58 kg of liquid water at 100°C. A radio rated at 100 watts operating for 10 hours continuously uses one kilowatt hour.

- 1 kWh = 3.6 x 10
^{6}J - 1 kWh = 8.6 x 10
^{5}cal - 1 kWh = 3412 BTU