What size power station do I need for a power outage?
The right size depends on what you must keep running and for how many days. This method gives you a number in watt-hours (Wh), which is how battery capacity is measured.
- List the devices you really need.
- Find each device’s average watts. The calculator has presets.
- Multiply watts by the hours per day you’ll use each device to get Wh per day.
- Add them up, then divide by 0.87 to account for inverter loss.
- Multiply by the number of days, then add about 20% as a safety buffer.
Example: an essentials day
| Device | Average watts | Hours per day | Wh per day |
|---|---|---|---|
| Full-size fridge | 52 W | 24 | about 1,260 Wh |
| Wi-Fi router + modem | 20 W | 24 | 480 Wh |
| Two phones charging | 15 W each | 1 | about 30 Wh |
| Three LED lights | 30 W total | 5 | 150 Wh |
| Laptop | 60 W | 4 | 240 Wh |
| Total | about 2,160 Wh |
Divided by 0.87, that’s about 2,480 Wh of battery per day. For three days, that’s roughly 7,450 Wh, or about 8,900 Wh with a 20% buffer. That is more than a single portable power station holds.
What most people do instead
Drop the fridge from the battery plan, or power it only in short cycles, and the same list falls to about 900 Wh per day, or about 1,035 Wh of battery. Three days then needs around 3,100 Wh, or about 3,700 Wh with a buffer. Adding solar panels to recharge during the day can cut the battery size you need, but it depends on sunlight.
Use the calculator to try your own list and see exactly how long your battery will last.