Energy calculator
Assumes constant power while operating; actual cycling appliances may use less.
Energy (kWh) = power (W) ÷ 1,000 × time (h)
Formula
Power in watts ÷ 1,000 × hours
How the calculation works
Estimate electrical energy in kilowatt-hours from watts and hours. Enter each measurement in the unit shown beside the input. The result updates when you change a value; incomplete or unsupported inputs display an explanation.
Worked example
A 1,000 W load operating for 3 hours uses 3 kWh.
When to use this calculator
Use this to compare energy use for loads with approximately constant power.
Common mistakes and limits
Watts describe a rate; kWh describes energy. Cycling devices need actual operating time.
Check your result
Check that all measurements describe the same object or time period. Repeat the calculation with unrounded values, then round only the final quantity to a precision suitable for the task.
Frequently asked questions
Does this calculator need an account?
No. Calculations run in your browser without an account.
How precise is the displayed result?
The display rounds to six decimal places. Measurement uncertainty can be larger than this rounding.
Sources & references
- Electrical Energy and Power — OpenStax
