Energy use Calculator: measuring notes and method
Use effective operating hours
Avoid reducing both power and runtime for the same duty cycle. Use either measured average power over elapsed hours or rated power over equivalent full-power hours.
Keep energy and charges separate
The kWh result can be multiplied by a unit energy rate. Fixed charges, varying tariffs and other billing components are not automatically included in that simple cost.
Formula
Energy (kWh) = power (W) ÷ 1000 × hours per day × days.
Product reference: Fluke electrical glossary
Worked example
Illustrative values match Reset example and stay fixed when you edit the calculator.
Starting-value worked example
- Appliance power
- 1,000 W
- Use per day
- 3 hours
- Number of days
- 30
Energy use: 90 kWh
Follow the calculation
- Power = 1,000 ÷ 1,000 = 1 kW.
- Time = 3 × 30 = 90 hours.
- Energy = 1 × 90 = 90 kWh.
Reviewed 19 October 2026. How calculations are checked · Report a correction