The kilowatt-hour (kWh) is a unit of energy. But how much? We have seen that: energy (kWh) = power (kW) × time (h) Normally we want energy in joules (J) and time in seconds (s). The kW above is 1000 W (1000 J/s). The hour is 3,600 seconds, so: 1 kWh = 1,000 J/s × 3,600 s 1 kWh = 3,600,000 J 1 kWh = 3·6 MJ (mega joules: see prefixes) The kWh is a large unit of energy used to measure how much energy is used in homes.
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