How it works
Runtime hours = battery Wh × usable fraction × efficiency ÷ load watts.
Input definitions
- Nominal battery energy (Wh)
- Enter the value in the labeled unit.
- Usable fraction (%)
- Enter the value in the labeled unit.
- Inverter efficiency (%)
- Enter the value in the labeled unit.
- Average load (W)
- Enter the value in the labeled unit.
A worked example
- Nominal battery energy (Wh)
- 1000
- Usable fraction (%)
- 70
- Inverter efficiency (%)
- 88
- Average load (W)
- 300
Assumptions & limits
Uses only the values entered. Rates are illustrative inputs, not live quotes, legal rules or personalised advice. Check provider terms, local requirements and measurements before acting.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-19. Content checked against the stated method and examples. Our verification approach.
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Common questions
Why can a UPS deliver less runtime?
High-rate battery capacity, ageing, temperature, inverter idle use and cutoff voltage reduce usable energy.
How does UPS runtime from watt-hours calculate the result?
Runtime hours = battery Wh × usable fraction × efficiency ÷ load watts.
What should I verify before using UPS runtime from watt-hours?
Uses only the values entered. Rates are illustrative inputs, not live quotes, legal rules or personalised advice. Check provider terms, local requirements and measurements before acting.