The kilowatt-hour
The home meter measures electrical energy in kilowatt-hours.
The kilowatt-hour
A kilowatt-hour (kWh) is the energy used by an appliance of power 1 kW in one hour. Energy is usually measured in joules, but a household's use is a huge number of joules, so the kWh is used as the unit for electricity.
1 kWh = 1 kW × 1 h
= 1000 W × 1 × 60 × 60 s
One unit of electricity
1 kWh = 3 600 000 J = 3.6 × 106 J
A watt for a second — a watt-second — is one joule.