Sizing a portable power station for a real outage

Start with a load list

Write down what you want to keep running and for how long. A refrigerator cycles rather than running continuously, a router draws very little, and a space heater draws a great deal. Add them up over a day, not over a minute.

Watt-hours versus watts

Watt-hours are capacity: how much energy the battery holds. Watts are output: how much can flow at once. A station can have generous capacity and still refuse to start a device that needs more output than its inverter provides.

Motors and compressors are the usual offenders, because they draw a surge when starting that is several times their running draw. Check the surge rating, not just the running rating.

Output quality and what will refuse to run

Most modern stations produce a pure sine wave, which electronics and motor-driven appliances expect. High-draw heating appliances are better run from a generator or left off entirely.

Chemistry and cycle life

Lithium iron phosphate batteries typically offer more charge cycles and better heat tolerance than nickel-based lithium cells, while weighing more for the same capacity. Also check how fast the station recharges from the wall or solar, and whether it can pass power through to a device while charging.

How we compare them

Our comparison rows cover capacity, continuous and surge output, chemistry and recharge time. See the portable power station comparison.