How long will your
backup battery last?
Estimate runtime from the battery's watt-hours and your equipment's power draw. Change every assumption to match your setup.
Estimated battery runtime
At a steady 75 W load
An energy estimate, not a guarantee or a compatibility check. Battery age, temperature, startup demand and other loads can change actual runtime.
Watts and watt-hours measure different things.
Watts measure the rate of power use. Watt-hours measure stored energy. A 500 Wh battery does not necessarily have a 500 W output rating.
Presets are editable midpoints from official average AC input ranges: Mini 20-40 W, Standard 4 75-100 W, and Standard Actuated 50-75 W. Measure your load when possible. Confirm input requirements separately.
340 Wh at 75 W lasts about 4 hours 32 minutes.
Usable capacity and conversion efficiency are separate allowances. If your battery's Wh figure already describes delivered usable energy, use 100% for both to avoid counting the same loss twice.
Starlink during a power cut
Can I enter a battery capacity in Ah?
Convert it to nominal Wh using the battery's rated voltage: Ah multiplied by volts. A capacity in Ah alone is not enough.
Does estimated runtime prove a power bank will work?
No. Your power source must also meet the kit's required voltage, output power and connection requirements.
Should I include other devices?
Yes. Add the average draw of any separate router, inverter overhead or other equipment using the same energy supply, without counting losses twice.
Will the load stay constant?
Not necessarily. Kit model, temperature and activity can change consumption. Use a measured average and allow for uncertainty.