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Calculators / Science / Battery runtime
Battery runtime calculator
Estimate device runtime from battery energy and load.
On this page
Nominal battery energy1,200Wh
Usable delivered energy864Wh
Estimated runtime7.2hours
Calculator controls
How to calculate
Estimate device runtime from battery energy and load.
runtime = voltage × amp-hours × usable fraction × efficiency ÷ load
Worked example
Battery voltage (V): 12; Battery capacity (Ah): 100; Average load (W): 120; Usable capacity (%): 80; System efficiency (%): 90.
Nominal battery energy: 1,200 Wh; Usable delivered energy: 864 Wh; Estimated runtime: 7.2 hours.
Assumptions and limits
Battery voltage varies with discharge, rated capacity depends on discharge rate and temperature, and inverter standby consumption may be significant.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Estimate device runtime from battery energy and load. The result follows the displayed formula and keeps every adjustable assumption visible.
When this tool is useful
Use this tool to plan quantities or compare scenarios before making a purchase or technical decision.
Understanding your inputs
| Input | What to enter |
|---|---|
| Battery voltage (V) | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Battery capacity (Ah) | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Average load (W) | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Usable capacity (%) | Enter a number of at least 0 and no more than 100. |
| System efficiency (%) | Enter a number of at least 0 and no more than 100. |
Frequently asked questions
What can change the battery runtime result?
Battery voltage varies with discharge, rated capacity depends on discharge rate and temperature, and inverter standby consumption may be significant.
Should I round the inputs first?
No. Enter the best measurements available and round only the practical final quantity, such as full packs, boards, sheets, or components.