Power station runtime calculator
Choose what you need to keep running in a power outage, on a camping trip or off-grid, and see how long a battery lasts, including every power station from our buying guides side by side.
1. What do you need to power?
Set how many of each device run at the same time. Watts are typical figures: edit them to match the label on yours.
- Refrigeratoraverage over a day (the compressor cycles on and off)1
- Chest freezeraverage over a day0
- Wi-Fi router + modem1
- CPAP (no humidifier)about 3× more with the heated humidifier on0
- Phone charging2
- Laptop0
- LED light bulb2
- TV (55-inch LED)0
- Box fan0
- Desktop PC + monitor0
- Electric blanket0
- Sump pump (while running)0
- Microwave0
- Coffee maker0
- Space heater0
- Window air conditioner0
2. Your result
3. How long each power station from our guides would last
Capacity and output from each maker's spec sheet. “Too small” means the load is above the station's continuous AC output.
How the calculator works
Runtime is the battery's usable energy divided by what your devices draw: hours = capacity (Wh) × 0.85 ÷ load (W). We count 85% of the rated capacity because the inverter that turns battery power into wall-socket power loses some as heat, and the battery keeps a small reserve. Real runtimes vary with temperature, battery age and how hard each device works, so treat the result as a planning estimate.
Two numbers matter when you choose a power station: capacity (Wh), which sets how long it lasts, and continuous AC output (W), which sets what it can run at all. Fridges, freezers, sump pumps and air conditioners also need a few seconds of much higher starting power, which is why the calculator shows a peak figure.
Typical power draw of common devices
| Device | Running watts | Starting watts | On 1,000 Wh |
|---|---|---|---|
| Refrigerator | 60 W | 1,200 W | 14 hours |
| Chest freezer | 40 W | 1,000 W | 21 hours |
| Wi-Fi router + modem | 15 W | — | 2 days 9 h |
| CPAP (no humidifier) | 30 W | — | 28 hours |
| Phone charging | 10 W | — | 3 days 13 h |
| Laptop | 50 W | — | 17 hours |
| LED light bulb | 9 W | — | 3 days 22 h |
| TV (55-inch LED) | 80 W | — | 11 hours |
| Box fan | 50 W | — | 17 hours |
| Desktop PC + monitor | 200 W | — | 4.3 hours |
| Electric blanket | 100 W | — | 8.5 hours |
| Sump pump (while running) | 800 W | 2,000 W | 1.1 hours |
| Microwave | 1000 W | — | 51 minutes |
| Coffee maker | 800 W | — | 1.1 hours |
| Space heater | 1500 W | — | 34 minutes |
| Window air conditioner | 600 W | 1,800 W | 1.4 hours |
Typical figures; the label on the device (or a plug-in power meter) gives the real number.
Frequently asked questions
How do I work out how long a power station will last?
Divide the usable capacity by the load: runtime (hours) = capacity (Wh) × 0.85 ÷ load (W). The 0.85 accounts for inverter losses and the reserve the battery keeps. A 1,000 Wh station running a 100 W load lasts about 8.5 hours.
How long will a power station run a refrigerator?
A typical full-size fridge averages about 60 W over a day because its compressor cycles on and off, so a 1,000 Wh station runs it for roughly 14 hours. The compressor needs a short burst of 1,000 W or more to start, so the station's surge rating has to cover that.
How long will a power station run a CPAP machine?
Without the heated humidifier a CPAP draws about 30 W, so a 1,000 Wh station lasts around 28 hours, or three to four nights. With the humidifier on, plan for about a third of that, or run the CPAP from the station's DC outlet with the maker's DC cable to waste less power.
What is the difference between Wh and W?
Watt-hours (Wh) is how much energy the battery stores, like the size of a fuel tank. Watts (W) is how fast a device uses it. A station also has a continuous output limit in watts: the devices running at the same time must stay below it, or the station shuts off.
Choosing a power station
Our guides compare power stations and backup batteries on capacity, output, battery chemistry and published expert scores: best home backup batteries for power outages, solar panels for power stations and UPS battery backups for computers and Wi-Fi.