Complete guide
Battery Runtime Calculator: formula, example and decision guide
Estimate usable energy and runtime from battery voltage, capacity, load and efficiency. The result updates instantly and keeps every assumption visible.
What the Battery Runtime Calculator measures
Estimate usable energy and runtime from battery voltage, capacity, load and efficiency.
Use the result to compare scenarios built from the same definitions and time period.
Formula and variables
The calculator applies runtime hours = voltage × amp-hours × efficiency × usable fraction ÷ watts. Each variable is entered in a labeled field and remains visible beside the answer.
runtime hours = voltage × amp-hours × efficiency × usable fraction ÷ wattsWorked example
12 V × 100 Ah at 90% efficiency and 80% usable capacity provides 864 Wh, or 2.88 hours at 300 W.
Change one input at a time to see which assumption has the greatest effect on the result.
How to interpret the result
Read the main result together with the detailed rows; the headline number alone does not describe every cost, unit or assumption.
Save comparable scenarios with the copy, link, CSV or PDF controls.
Assumptions and limitations
Temperature, aging, discharge rate, inverter idle draw and battery management limits change real runtime.
Real contracts, measurements, platform rules and professional standards can add inputs that this general-purpose model does not infer.
Accuracy checklist
Confirm units, time periods, fees and source figures before relying on the output.
Round the displayed answer only after the calculation; intermediate values retain full precision.
Calculation audit
| Item | What to review |
|---|---|
| Inputs | Battery voltage (V), Battery capacity (Ah), Average load (W), System efficiency (%), Usable depth of discharge (%) |
| Equation | runtime hours = voltage × amp-hours × efficiency × usable fraction ÷ watts |
| Example | 12 V × 100 Ah at 90% efficiency and 80% usable capacity provides 864 Wh, or 2.88 hours at 300 W. |
| Limit | Temperature, aging, discharge rate, inverter idle draw and battery management limits change real runtime. |
Frequently asked questions
What does this Battery Runtime Calculator calculate?
Estimate usable energy and runtime from battery voltage, capacity, load and efficiency.
Which formula does it use?
runtime hours = voltage × amp-hours × efficiency × usable fraction ÷ watts
Does it calculate while I type?
Yes. Valid changes update the result automatically without reloading the page.
Which inputs should I verify?
Verify every unit, period, rate and fee against the source you are modeling.
Is the result exact?
Temperature, aging, discharge rate, inverter idle draw and battery management limits change real runtime.
Can I save or share the result?
Yes. Copy, native sharing, WhatsApp, PDF/Print, CSV, comparison and parameterized links are available.
What to keep in mind
Temperature, aging, discharge rate, inverter idle draw and battery management limits change real runtime.
Results display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.