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Transferring Electrical Energy

The power or a device is measured in watts (W). A kilowatt means 1000 watts.

Energy is normally measured in joules (J) but when calculating the cost of using electricity energy is measure in kilowatt-hours (kWh).

Energy transfered                =                power             x       time

(kilowatt-hours, kWh)                 (kilowatts, kW)            (hours, h)

Total cost

total cost      =      number of kilowatt-hours       x          cost of one kilowatt-hour

Example; If a 3 kW heater is used for 2 hours what was the total cost if every kW h of electricity costs 7 pence ?

cost calculation