Power Station Runtime Calculator
Find out exactly how long your power station will power your devices. Enter its capacity in watt-hours, choose a realistic efficiency, add the devices you plan to run — and get an instant, visual runtime estimate below.
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Enter your power station’s capacity in Wh to see a runtime estimate.
This is an estimate. Real-world runtime can be lower than the theoretical figure due to inverter efficiency losses, fluctuating (not constant) device draw, ambient temperature, battery age/health, and other factors. Always check your power station’s official specifications before relying on it for critical use.
How the runtime calculation works
The calculator uses two simple, standard steps. First, it works out the usable energy in your battery, since no inverter or battery system is 100% efficient:
Usable Energy (Wh) = Battery Capacity (Wh) × Efficiency
Then it divides that usable energy by your total connected load to get the runtime:
Runtime (hours) = Usable Energy (Wh) ÷ Total Power Consumption (W)
That decimal-hour figure is then converted into a readable format like "7h 15m" so it actually means something at a glance.
Worked example
Say you have a 1000 Wh power station running at 85% efficiency, powering a refrigerator (150 W) and a Wi-Fi router (10 W) — a total load of 160 W.
Usable energy: 1000 × 0.85 = 850 Wh. Runtime: 850 ÷ 160 = 5.31 hours, or 5h 19m. Add a second device and the runtime drops accordingly — this is exactly what the calculator above computes as you check boxes and adjust quantities.
Tips for a more accurate estimate
A few adjustments make the estimate track reality more closely:
- Edit the wattage field for any device to match the number printed on its label or manual — our defaults are typical values, not your exact unit.
- Remember that devices with compressors or motors (fridges, AC units, pumps) draw a brief high startup surge above their running watts — check your power station's surge rating separately.
- Lower the efficiency slider if your power station is older or you're running it through a long/thin extension cable, both of which increase losses.
- Add a 10–20% safety margin to any runtime you're depending on for something important, like medical equipment or food safety.
Frequently asked questions
Does the runtime calculator account for battery degradation?
Not directly — the formula assumes your battery is at or near its rated capacity. Lithium batteries typically retain 80%+ of their original capacity for hundreds of charge cycles, but older or heavily used units will run for less time than a brand-new one at the same stated Wh. If your power station is a few years old, consider lowering the efficiency value or the capacity figure slightly to compensate.
Should I use running watts or surge watts in the calculator?
Use running (continuous) watts — that's what determines how long the battery lasts. Surge watts only matter for the split-second a motor or compressor starts, and they determine whether your power station's inverter can start the device at all, not how long it will run it.
Can I calculate runtime for multiple devices running at different times?
This calculator estimates simultaneous, continuous use of everything you select. For devices that cycle on and off (like a fridge) or run only part of the time, you can approximate by lowering the wattage field to reflect an average draw over time, rather than its full running watts.
Why does my power station's app or screen show a different runtime?
Many power stations estimate runtime internally using real-time current draw and battery voltage, which reacts to actual conditions (temperature, exact load, battery state of charge) — it's often more accurate in the moment than any generic formula, ours included. Use this calculator for planning ahead of time, and trust your unit's live readout once devices are actually connected.
What efficiency percentage should I choose?
85% is a reasonable default for most modern portable power stations. Choose 90% for newer, higher-end units with efficient pure sine wave inverters, or 80% for older/budget units or when running through additional cables or adapters. If you know your manufacturer's stated round-trip efficiency, enter it directly using the "Custom" option.