What is the commercial unit of electrical energy?

The commercial unit of electrical energy is the kilowatt-hour (kWh).

One kilowatt-hour is defined as the energy consumed when an electrical device of power 1 kilowatt (1000 watts) operates for 1 hour.

Mathematically:
1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ joules

This unit is widely used by electricity distribution companies for billing purposes, as it represents practical energy consumption in homes, industries, and commercial establishments.

For example, if a 1000 W appliance runs for 1 hour, it consumes 1 kWh of electrical energy.