How to use it
- Enter capacity and choose Wh or Ah.
- If using Ah, enter the nominal battery voltage.
- Enter load power and estimated efficiency, then calculate.
Battery Runtime Calculator
Estimate idealized battery runtime from capacity, load and efficiency.
Important: This calculator is for educational and estimation purposes only. It is not electrical safety, installation, engineering, or code-compliance advice. Always consult a qualified electrician or engineer for real-world electrical work.
About the Battery Runtime Calculator
This calculator converts battery capacity into an idealized usable-energy estimate and divides it by load power.
How it works
For Ah input, nominal Wh equals Ah × V. Usable Wh equals nominal Wh × efficiency, and runtime hours equals usable Wh ÷ load watts.
Example
A 1,000 Wh battery at 90% estimated efficiency supplies 900 usable Wh, which is an idealized 9 hours at a constant 100 W load.
Notes
Real runtime varies with battery chemistry, discharge rate, temperature, aging, cutoff voltage, conversion losses and changing load.