Power Energy
Electrical Consumption and Cost
Electrical consumption is the energy used over a period, obtained by multiplying power by time. Tariffs are normally expressed per kilowatt-hour, so the energy charge is the consumption in kilowatt-hours multiplied by the rate. The estimate assumes constant power and a single rate; tariffs with time bands or standing charges need a more detailed calculation.
Electrical Consumption and Cost
E = P × t; cost = E × rate
Variables and units
| Symbol | Quantity | Unit |
|---|---|---|
| E | Energy consumed | kWh |
| P | Power | kW |
| t | Time | h |
| rate | Price per kilowatt-hour | currency/kWh |
Conditions of application
Constant power and a single tariff. Real bills may include standing charges, taxes, time-of-use tariffs and tiered rates, so the result is an estimate of the energy charge only.
Worked example
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Convert power and time into watt-hours, kilowatt-hours and energy cost.