1 kilowatt-hour (kWh) is equal to ____.

The correct answer is Option (4) → \(3.6\times10^{6}\) joule

A kilowatt-hour is the energy used by a 1 kW device running for 1 hour. Energy = power × time, with the power in watts and the time in seconds.

• 1 kW \(=1000\) W and 1 h \(=3600\) s

• 1 kWh \(=1000\times3600=3{,}600{,}000\) J \(=3.6\times10^{6}\) J

Tip: The kilowatt-hour is the “unit” on an electricity bill; 1 unit = 1 kWh = \(3.6\times10^{6}\) J is worth memorising.