How to size a portable power station
Two numbers decide whether a station fits: capacity (watt-hours, how much energy it stores) and output (watts, how much it can deliver at once). Pick for both.
1. Add up your daily energy
For each appliance, multiply watts by hours of use per day. Here’s the calculator’s power-outage example:
| Appliance | Watts | Hours/day | Qty | Wh/day |
|---|---|---|---|---|
| Refrigerator (full size) | 60 | 24 | 1 | 1,440 |
| Wi-Fi router and modem | 15 | 24 | 1 | 360 |
| Phone charging | 15 | 2 | 2 | 60 |
| LED light bulb | 10 | 5 | 3 | 150 |
| Total | 2,010 |
2. Allow for losses
About 85% of the rated capacity reaches AC appliances. Divide by that: 2,010 ÷ 0.85 = 2,365 Wh of rated capacity for one day. Multiply by the number of days you want to cover.
3. Check the output
Add up the watts of everything that could run at the same time (135 W here). The station’s continuous output must be above that. Things with motors or compressors also need surge headroom when they start; the fridge in this example can briefly push the peak to about 1,275 W.
4. Consider solar for anything longer than a day or two
A panel’s real output is usually around 75% of its rating. Daily solar energy ≈ panel watts × peak sun hours × 0.75. If that covers your daily use, the station can keep going as long as the sun cooperates.
Battery chemistry
Most current stations use LiFePO4 (lithium iron phosphate) cells, rated for thousands of charge cycles, against a few hundred for older NMC packs. For backup power you’ll use for years, LiFePO4 is the safer choice.