Runtime of a 300 Wh power station, by device
At 85% usable capacity (255 Wh), without recharging. Real runtime depends on the actual draw of your device, which you can measure with a plug-in watt meter.
| Device | Typical watts | Runtime |
|---|---|---|
| LED light bulb | 9 W | 28.3 h |
| Phone charger | 15 W | 17.0 h |
| Wi-Fi router and modem | 15 W | 17.0 h |
| CPAP machine | 40 W | 6.4 h |
| Mini fridge (average) | 30 W | 8.5 h |
| Full-size refrigerator (average) | 60 W | 4.3 h |
| Laptop | 60 W | 4.3 h |
| Box fan | 50 W | 5.1 h |
| LED TV | 100 W | 2.6 h |
| Desktop computer | 200 W | 1.3 h |
| Microwave | 1,000 W | 15 min |
| Coffee maker | 1,000 W | 15 min |
| Space heater | 1,500 W | 10 min |
Is 300 Wh enough?
This is a small unit for phones, laptops, lights and a CPAP for a night. It will not keep a refrigerator going for long. For a full plan, see the power station sizing guide, and the size calculator to work out your own daily energy.
Want to change anything else? The calculator above is the full Battery & Power Station Runtime Calculator: edit any number and the results update instantly.
Tools & materials for this project
As an Amazon Associate we earn from qualifying purchases. These links do not change what you pay.
Frequently asked questions
How long will a 300Wh power station run a refrigerator?
A full-size fridge averages about 60 W over a day, so 300 Wh (255 Wh usable) runs it for roughly 4.3 h. Older or larger fridges use more, so the time can be shorter.
How many times will a 300Wh power station charge a phone?
About 17 full charges, at about 15 Wh of battery per phone, before losses in charging.
How long will a 300Wh power station run a CPAP?
About 6.4 h at 40 W, which is 0.8 nights of 8 hours. Using the humidifier raises the draw.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.