Battery Runtime Calculator
Enter a battery's capacity and voltage, your load, and depth of discharge to estimate its runtime.
Battery Runtime Calculator
Results
- Total energy
- 1200 Wh
- Usable energy
- 864 Wh
- Estimated runtime
- 8h 38min
How to estimate battery runtime
Enter a battery's capacity and voltage, your load, and how deeply you're willing to discharge it to estimate how long it will run.
The formula
- Formula
runtime_h = (Ah × V × DoD × efficiency) / load_W
Depth of discharge, explained
Depth of discharge (DoD) is how much of a battery's rated capacity is safe to actually use. Lead-acid batteries are typically limited to 50% DoD to preserve their lifespan; lithium (LiFePO4) chemistries tolerate 80–100% DoD without significant degradation.
How to use it
- Enter the battery's capacity in amp-hours and its voltage.
- Enter the load in watts (from the device's rating, or amps × volts).
- Set the depth of discharge and system efficiency for your setup.
Privacy
Runs locally in your browser. No data is sent to the server.
FAQ
What DoD should I use for my battery?
About 50% for lead-acid (flooded or AGM), and 80–100% for lithium (LiFePO4) — check your battery's datasheet for its specific recommendation.
Does temperature affect real-world runtime?
Yes, meaningfully — cold temperatures reduce a battery's effective capacity, sometimes substantially. This calculator assumes room-temperature, rated capacity.
What does "system efficiency" account for?
Losses in the inverter (if you're running AC loads) and wiring between the battery and the load — 90% is a reasonable default for a well-sized system.