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Energy used
Turn a power rating and a duration into the energy the meter records. The division by 1000 converts watts into kilowatts.
The Formula
kWh = watts x hours / 1000
Turn a power rating and a duration into the energy the meter records. The division by 1000 converts watts into kilowatts.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| W | Power rating in watts | watts | The figure on the appliance label; a rate, not a quantity. |
| h | Hours of use | hours | Actual running time, which for cycling appliances is less than the hours it is switched on. |
| kWh | Energy consumed | kilowatt-hours | The quantity the bill charges for, regardless of how it was reached. |
What Each Symbol Means
Wwatts
Power rating in watts
The figure on the appliance label; a rate, not a quantity.
hhours
Hours of use
Actual running time, which for cycling appliances is less than the hours it is switched on.
kWhkilowatt-hours
Energy consumed
The quantity the bill charges for, regardless of how it was reached.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate electricity cost page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Electricity Cost, filed under Everyday Life. Every number the guide produces comes from substituting into this one line.