Example 1
A 100 W lamp running for 3 h uses 300 Wh = 0.3 kWh = 1.08 MJ.
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Physics tools › Electric energy, power and time
Mendeleev · Physics
Electric energy, power and time
Energy is power accumulated over time. The joule is the SI unit; watt-hours and kilowatt-hours are convenient when power is expressed in watts and time in hours.
Formula usedE = PΔt
Calculate
Electric energy, power and time
What do the symbols mean?
Eenergy
Ppower
Δtelapsed time
Two worked examples
Example 2
A 2 kW heater using 6 kWh of energy has operated for 3 h.
Good to know The formula E = PΔt links transferred energy, power and time. The calculator handles the unit conversions.