battery runtime calculator
Battery Runtime Calculator
Battery labels are only the start. This page explains why usable watt-hours are lower than nominal capacity.
Calculator
Start with a quick estimate, then switch to Advanced if you need multiple devices, startup surge, battery health, or cold-weather loss.
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Output path
Estimated runtime
13h 3mThis setup has comfortable headroom for overnight use, assuming the wattage estimate is realistic.
Usable energy783 Wh
Average load60 W
Running watts60 W
Max surgen/a
Conservative8h 10m
Estimated13h 3m
Optimistic16h 13m
- 1024 Wh nominal battery capacity
- AC inverter output path
- 85% conversion efficiency
- 10% reserve kept unused
- 60 W average load from 1 load
- 100% battery health
- 0% temperature loss
- This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior.
Source-Backed Next Steps
Smallest matching recordJackery Explorer 600 v2Best for
Understand the formula and calculate hours from Wh and W.
Inputs to check
- Battery capacity in watt-hours.
- Measured or realistic device watts.
- Efficiency, reserve, duty cycle, and output path.
Before relying on it
- Check startup surge for motors and compressors.
- Use a watt meter for critical outage or medical-adjacent loads.
- Keep source confidence visible when comparing models.
This calculator gives a planning estimate. Treat the result as a starting point, then refine it with measured watts, the device manual, and the station's current output limits.
Related Calculators
Use the related tools when charging, sizing, surge, or power path changes the answer.
FAQ
These answers keep the estimate grounded in assumptions instead of pretending runtime is exact.
How do you calculate portable power station runtime?
Use usable watt-hours divided by average load watts. For AC loads, a practical first-pass formula is battery Wh x efficiency x reserve factor divided by device watts.
Why is real runtime lower than the label capacity?
Battery label capacity is nominal. Inverter losses, DC conversion losses, reserve settings, cold weather, battery age, and changing device loads all reduce real runtime.
What efficiency should I use for AC devices?
Use 80% to 90% for most AC inverter loads unless you have measured data. The default calculator value is 85%.
What efficiency should I use for DC devices?
DC loads can often do better than AC because the inverter stays off. Use 88% to 95% only when the voltage path is appropriate and the device is stable.
Can a power station run a refrigerator overnight?
Often yes, but the answer depends on battery Wh, fridge running watts, compressor duty cycle, room temperature, and startup surge. Always check surge capability.
Why does the fridge setting use a duty cycle?
Refrigerator compressors cycle on and off. The calculator uses duty cycle to convert running watts into a more realistic average load.
How many watt-hours does a CPAP need overnight?
A CPAP without heated humidification may use roughly 240 to 480 Wh over eight hours. Heated humidifiers and tubes can raise that substantially.
Can I use this for medical backup planning?
Use it only as a planning estimate. For medical devices, follow the manufacturer guidance and keep a tested backup plan.