How it works
Usable energy Wh = capacity Ah × nominal V × usable fraction × efficiency. Runtime hours = usable Wh/load W.
Input definitions
- Battery capacity (Ah)
- Enter the value in the labeled unit.
- Nominal voltage (V)
- Enter the value in the labeled unit.
- Usable capacity share (%)
- Enter the value in the labeled unit.
- Conversion efficiency (%)
- Enter the value in the labeled unit.
- Constant load power (W)
- Enter the value in the labeled unit.
A worked example
- Battery capacity (Ah)
- 100
- Nominal voltage (V)
- 12
- Usable capacity share (%)
- 80
- Conversion efficiency (%)
- 90
- Constant load power (W)
- 100
Assumptions & limits
No battery wiring, charging or protection design. Enter realistic manufacturer data and permitted usable capacity.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-17. Content checked against the stated method and examples. Our verification approach.
Common questions
Why might actual battery runtime be shorter?
Nominal amp-hours and voltage are simplified values. Discharge rate, temperature, age, protection cutoffs and inverter idle losses can reduce delivered energy.
How does Battery runtime from capacity and load work?
Usable energy Wh = capacity Ah × nominal V × usable fraction × efficiency. Runtime hours = usable Wh/load W.
What are the limits of Battery runtime from capacity and load?
No battery wiring, charging or protection design. Enter realistic manufacturer data and permitted usable capacity.