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 (kW h).
kWh = (Watt x hour ) / 1000
What is 1 kW h?
Let us say we have a machine that uses 1000 J of energy every second. If this machine is used continuously
for one hour, it will consume 1 kW h of energy. Thus, 1 kW h is the energy used in one hour
at the rate of 1000 J s–1 (or 1 kW).
1 kW h = 1 kW ×1 h
= 1000 W × 3600 s
= 3600000 J
1 kW h = 3.6 × 106 J.
The energy used in households, industries and commercial establishments are usually expressed in kilowatt hour. For example, electrical energy used during a month is expressed in terms of ‘units’.
Here, 1 ‘unit’ means 1 kilowatt hour.