Commercial unit of energy
The unit joule is too small and hence is inconvenient to express large quantities of energy. We use a bigger unit of energy called kilowatt hour (kWh).
Thus, 1 kilowatt hour = 1 Kilowatt for 1 hour at the rate of 1000 J s-1 (or 1 kW).
1 kWh = 1 kW × 1 h
= 1000 W × 3600 s
= 3600000 J
1 kWh = 3.6 × 106 J.
The energy used in households, industries and commercial establishments are usually expressed in kilowatt hour. Example :- electrical energy used during a month is expressed in terms of ‘units’. 1 unit means 1 kilowatt hour.
