--- title: "Power Station Runtime Calculator: Wh to Hours" description: "How long will a portable power station run your fridge, CPAP or laptop? Enter its Wh capacity and the load to get the runtime on AC or DC output." canonical: https://batteryruntimecalculator.com/power-station-runtime-calculator language: en updated: 2026-11-10 source_revision: 59f9d32 maintainer: Battery Runtime Calculator (hello@batteryruntimecalculator.com) --- # Power Station Runtime Calculator See how long a portable power station will run your fridge, CPAP, laptop or TV. Updated November 10, 2026 Quick answer Runtime ≈ capacity (Wh) × 0.85 ÷ load (W) on the AC outlets. A 1,000 Wh power station runs a 100 W load for about **8 h 9 min**, and a 65 W average fridge for about **12 h 48 min**. Estimated runtime 8 h 9 min ≈ 8.14 hours on 1,000 Wh at 100 W Usable energy 1,000 Wh Rated capacity 1,000 Wh Power from battery 118 W Discharge rate 0.12C How this was worked out 1. Battery energy: 1,000 Wh rated 2. Power drawn from the battery: 100 W ÷ 85% efficiency = 118 W 3. Rate effect (Peukert 1.05): the battery delivers 96% of its rating at this load 4. Runtime: 1,000 Wh × 96% × 100% usable ÷ 118 W = 8.14 h Runtime at other loads | Load | Runtime | | --- | --- | | 25 W | 34 h | | 50 W | 16 h 52 min | | 100 W | 8 h 9 min | | 150 W | 5 h 19 min | | 200 W | 3 h 56 min | ## Power station runtime chart Estimated runtime on the AC outlets for common power station sizes, at 85% inverter efficiency. | Device | 300 Wh | 500 Wh | 1000 Wh | 2000 Wh | | --- | --- | --- | --- | --- | | Phone charging (10 W) | 25 h 30 min | 42 h 30 min | 3 days 13 h | 7 days 2 h | | CPAP, no humidifier (40 W) | 6 h 1 min | 10 h 18 min | 21 h 15 min | 42 h 30 min | | Laptop (60 W) | 3 h 56 min | 6 h 44 min | 13 h 55 min | 28 h 20 min | | Full-size fridge, average (65 W) | 3 h 37 min | 6 h 11 min | 12 h 48 min | 26 h 9 min | | TV (100 W) | 2 h 18 min | 3 h 56 min | 8 h 9 min | 16 h 52 min | | Space heater, low (750 W) | 17 min | 28 min | 59 min | 2 h 2 min | ## How to work out power station runtime ``` Runtime (h) = capacity (Wh) × efficiency ÷ load (W) ``` 1. Find the capacity in Wh on the spec sheet. If it is only given in mAh, multiply by the cell voltage (often 3.2 V or 3.7 V) and divide by 1,000. 2. Add up the running watts of everything plugged in at the same time. For appliances that cycle, like fridges, use the daily average. 3. Multiply the capacity by 0.85 for AC outlets or 0.95 for DC outlets, and divide by the load. Power stations use lithium cells that deliver close to their full rating even at high loads, so a power station’s runtime stays predictable from 10 W to its maximum output. The calculator still applies a small Peukert correction for heavy loads. For the full method, see [how battery runtime is calculated](https://batteryruntimecalculator.com/how-battery-runtime-is-calculated). ## Watts, surge and runtime are three different limits - **Capacity (Wh)** sets how long it runs. - **Rated output (W)** sets the largest load it can power continuously. A 1,000 Wh station rated at 1,000 W cannot run a 1,500 W kettle, however full it is. - **Surge (W)** covers the brief start-up spike of motors and compressors. Fridges, pumps and power tools need it. To size a station for a set number of hours, use the [battery size calculator](https://batteryruntimecalculator.com/battery-size-calculator). If you are building your own system with separate batteries, the [12V battery runtime calculator](https://batteryruntimecalculator.com/12v-battery-runtime-calculator) and [solar battery calculator](https://batteryruntimecalculator.com/solar-battery-calculator) fit better. ## Frequently asked questions ### How long will a power station run a fridge? A full-size fridge averages about 50–80 W over a day as its compressor cycles. A 1,000 Wh power station runs one for about 12 h 48 min, and a 2,000 Wh unit about 26 h 9 min. Check the station can handle the fridge’s start-up surge, often 3–5 times its running watts. ### How long will a power station run a CPAP? A CPAP without the heated humidifier draws about 30–60 W. At 40 W, a 500 Wh power station lasts about 10 h 18 min, or about 11 h 34 min using the 12 V DC outlet with the maker’s DC adapter. Turning the humidifier on can triple the draw. ### Why does my power station not last as long as its Wh rating suggests? The Wh rating is the energy stored in the cells. Converting it to 120 V or 230 V AC loses roughly 10–20%, and the inverter draws a few watts even at idle. That is why a 1,000 Wh station delivers about 850 Wh to AC appliances. DC and USB outlets waste less. ### Is it better to use the AC or DC outlet? DC outlets (12 V car socket, USB-C) skip the inverter, so a device that can run on DC lasts roughly 10% longer. Laptops on USB-C, 12 V fridges and CPAP machines with a DC adapter are the usual examples. ### What size power station do I need? Multiply the watts of what you want to run by the hours you need, then divide by 0.85 for AC losses. Running 100 W for 10 hours needs about 1,200 Wh. 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