Power Station Runtime Calculator: How Long Will It Run?
Divide the station’s capacity in watt-hours by the watts your devices draw, then multiply by about 0.85 to account for inverter losses. A 1,000 Wh station running a 100 W load lasts about 8.5 hours. Use the calculator below to add several devices, switch between AC and DC outputs, and check whether your station can handle the load at all.
Fridge, freezer or TV? Convert the EnergyGuide label (kWh/year) to average watts
How the calculator works
The calculator uses the same formula you can do on paper:
runtime (h) = battery Wh × efficiency ÷ total load W
Example: 1,000 Wh × 0.85 ÷ 100 W = 8.5 hours
- Battery capacity (Wh) is the number on the station’s spec sheet, usually printed on the box too.
- Efficiency covers the energy lost when the station converts battery power into what your device uses. We use 0.85 for the AC outlets, because the inverter that creates household-style power wastes some energy as heat. For DC and USB ports we use 0.90. Both are planning assumptions, not measured values for any specific model. If your station’s manual lists an efficiency, use the custom option.
- Total load (W) is the sum of everything plugged in at the same time.
If you enter hours per day for each device, the calculator also tells you how many days the charge lasts with your real routine. It uses the same idea, based on daily energy: watts × hours of use.
The watts printed on a device’s label or power adapter are usually its maximum draw, according to the U.S. Department of Energy. Many devices use less most of the time, so a result based on label watts tends to be on the safe side.
Fridges, freezers and other devices that cycle
A refrigerator doesn’t draw its full power all the time. Its compressor turns on and off to hold the temperature. The Department of Energy suggests assuming a fridge runs at its maximum wattage about one third of the time it’s plugged in.
There’s a more precise shortcut. New fridges, freezers and TVs sold in the U.S. carry a yellow EnergyGuide label with their estimated yearly energy use in kWh. Convert it to average watts:
average W = kWh per year × 1,000 ÷ 8,760 hours
Example: a fridge rated 450 kWh/year averages 450 × 1,000 ÷ 8,760 = 51.4 W. On a 1,000 Wh station: 1,000 × 0.85 ÷ 51.4 = about 16.5 hours.
The label value comes from a standard test. A fridge in a hot garage, opened often or packed with warm food will use more. For typical figures by fridge type, based on ENERGY STAR data, see Can a Portable Power Station Run a Refrigerator?
Quick reference: runtime by capacity and load
Estimated runtime from the AC outlets with 0.85 efficiency and a constant load:
| Load | 300 Wh | 500 Wh | 1,000 Wh | 2,000 Wh | 3,000 Wh |
|---|---|---|---|---|---|
| 10 W | 26 h | 43 h | 85 h | 170 h | 255 h |
| 50 W | 5.1 h | 8.5 h | 17 h | 34 h | 51 h |
| 100 W | 2.5 h | 4.3 h | 8.5 h | 17 h | 26 h |
| 300 W | 51 min | 1.4 h | 2.8 h | 5.7 h | 8.5 h |
| 500 W | 31 min | 51 min | 1.7 h | 3.4 h | 5.1 h |
| 1,000 W | 15 min | 26 min | 51 min | 1.7 h | 2.5 h |
Small stations often can’t deliver 500 W or 1,000 W at all. Check the rated continuous output before relying on those rows.
Power draw of common devices
These values come from the manufacturers’ published specifications. Specs checked on September 26, 2026 from the manufacturer’s page.
| Device | Published power figure | Source |
|---|---|---|
| Starlink Standard kit | 75–100 W average | Starlink Standard specification sheet |
| Starlink Mini | 25–40 W average | Starlink Mini specification sheet |
| MacBook Air 13″ and 15″ | 40 W adapter, up to 60 W | Apple MacBook Air tech specs |
For anything else, look at the label on the device or its power adapter. If it only lists amps, multiply by the voltage: 120 V for most U.S. household devices. For example, 0.5 A × 120 V = 60 W.
Can your station handle the load?
Runtime is only half the question. Every station has a rated continuous output in watts (for example, 1,800 W) and a higher surge rating that it can hold for a moment. If the total load is above the continuous rating, the station will shut off or refuse to power everything at once. Enter the rating in the calculator to get a warning.
Devices with motors or compressors, such as fridges, pumps and power tools, can pull several times their running watts for a moment when they start. The station’s surge rating has to cover that spike. Check the device’s manual for its starting watts and compare them with the station’s surge figure.
Safety: Don’t connect a portable power station to your home’s electrical panel or wiring yourself. That requires a transfer switch or inlet installed by a licensed electrician. Keep the station within the temperature range in its manual, and never exceed its rated output.
Why real runtime is often shorter
- Temperature: batteries deliver less energy outside their comfortable range. Check the operating and charging temperatures in your station’s manual.
- Battery age: every battery loses capacity over its charge cycles.
- Standby draw: leaving the AC inverter on uses some power even with nothing plugged in. Turn it off when you don’t need it.
- Low-battery cutoff: many stations stop before reaching exactly 0% to protect the battery.
For planning, treat the result as a best case and keep a safety margin. We suggest planning for at least 20% less runtime than the calculator shows; that figure is our rule of thumb, not a measured value. To see where our numbers come from, read How We Research.