Battery Runtime Calculator
Estimate how long a battery can support a steady electrical load using nominal voltage, amp-hour capacity, usable depth of discharge and system efficiency. It is a planning approximation for batteries, UPS systems and DC power applications.
Real runtime depends on chemistry, discharge rate, temperature, age, inverter behavior and manufacturer limits.
How this tool works
Usable energy ≈ voltage × amp-hours × usable fraction × efficiency. Runtime hours = usable watt-hours ÷ load watts.
Example
A 12 V, 100 Ah battery with 80% usable depth and 90% conversion efficiency provides about 864 Wh of usable energy, or roughly 4.3 hours at a 200 W load.
Common questions
Will a real battery run exactly this long?
No. Capacity varies with discharge rate, temperature, age, chemistry, inverter behavior and manufacturer limits.
What does usable depth mean?
It is the fraction of nominal battery capacity you plan to use before stopping discharge.