Power Station Runtime Calculator

Your estimate

Updates as you type. Estimates only.

Estimated runtime

9 h 43 min

9.7 hours

Total load: 88 W
Usable energy: 950 Wh
Energy delivered to devices: 855 Wh; After usable-capacity and conversion losses.

How this calculator works

Usable energy (Wh)    = rated capacity (Wh) × usable capacity (%)
Delivered energy (Wh) = usable energy × conversion efficiency (%)
Runtime (hours)       = delivered energy ÷ total load (W)

The default 95% usable capacity × 90% efficiency (≈ 85.5% combined) is in line with the combined factor of about 0.85 that several power station makers use in their own runtime formulas for AC devices. See the methodology for sources.

Worked example

Example (estimate). A hypothetical 1,000 Wh power station running a 60 W electric fan and a 10 W Wi-Fi router:

Usable energy: 1,000 × 95% = 950 Wh
Delivered after conversion losses: 950 × 90% = 855 Wh
Runtime: 855 Wh ÷ 70 W ≈ 12 h 13 min

Why real runtime may differ

Inverter losses change with load. Inverters are usually least efficient at very light loads, and the inverter draws some power even when idle.
DC outputs lose less. Powering a router or phone from 12 V or USB ports skips the DC-to-AC conversion and can extend runtime — try a higher efficiency for DC-only loads.
Devices don’t draw a steady wattage. Fans with speed settings, laptops charging and fridges cycling all vary.
Temperature and age. Heat triggers protective throttling, and batteries lose capacity as they age.

Check the output limits too

Runtime is only half the question. A power station also has a continuous output rating (the most it can supply steadily) and a surge rating (a brief peak). Motors and compressors — fridges, freezers, pumps, some fans — can draw several times their running power for a moment when they start. If the total load or the start-up surge exceeds the ratings, the unit may shut off. Enter the continuous output above to get a warning.

Safety. Follow the manufacturer’s instructions, keep the unit ventilated and dry, and never connect a power station or generator to your home’s wiring without a proper transfer switch installed by a licensed electrician.

Planning for outages? Read how to calculate power station runtime and choosing backup power for Philippine brownouts.

Frequently asked questions

How do I convert mAh to Wh?

Wh = mAh × volts ÷ 1,000. Use the battery’s nominal voltage, not the 5 V USB output. A power bank rated 20,000 mAh at 3.7 V holds about 74 Wh.

Can a portable power station run a refrigerator?

Often yes, if its continuous and surge output can handle the fridge’s start-up and its capacity covers the fridge’s average consumption. Use the fridge’s measured or label kWh to estimate average watts (monthly kWh × 1,000 ÷ 720 hours), not the nameplate wattage. Check the manufacturer’s guidance for compressor loads.

Can a power station run an aircon?

Only large units can, and usually not for long: an aircon’s power input is high relative to typical portable battery capacities. Enter your aircon’s power input above to see the estimated runtime, and check the continuous output rating.

Why is my real runtime shorter than the estimate?

Common reasons: devices drawing more than their label, the inverter’s own idle consumption, high temperatures, an ageing battery, and running near the inverter’s limit. Treat the estimate as a best case.