Portable Power Station Size Calculator
| Use case | Real load | Label size to buy |
|---|---|---|
| Camping weekend, two people | ~300 Wh | 500 Wh |
| Outage essentials, one night | ~550 Wh | 700 Wh |
| Fridge through a day outage | ~1,000 Wh | 1,500 Wh |
| Work-from-home day (laptop+router+light) | ~600 Wh | 1,000 Wh |
Power stations sell watt-hours, and every device you own eats them at a rate you can look up or estimate: a phone charges on 20, a CPAP breathes through 300 a night, a full-size refrigerator cycles through about 1,000 a day. Size the station by adding the load and multiplying by hours - then buy 25 percent more than the arithmetic says.
Bottom line: a camping weekend for two (phones, lights, a speaker, a cooler) lives comfortably in 300 to 500 Wh; one night of outage essentials (CPAP, phones, a lamp, the router) needs 500 to 700; keeping a refrigerator alive through a day-long outage pushes past 1,000 Wh and starts competing with a generator on price.
The honest part: two deratings shrink every unit's label - inverters lose 10 to 15 percent converting DC to AC, and manufacturers quote capacity at 100 percent depth of discharge while most units protect their batteries at 80 to 90 percent. The 80 percent rule absorbs both: size to 80 percent of the label and the spec sheet stops lying to you.
How to use
- List what you will actually run and for how long - the phone-and-lights list, not the if-the-power-dies wish list.
- Multiply each device's watts by hours to watt-hours, add them, and divide by 0.8 for the derating reality of inverters and battery protection.
- Read the nearest label size up - stations cluster at 300, 500, 700, 1,000, 1,500 and 2,000 Wh - and check the inverter rating covers your biggest single device's surge.
Frequently asked questions
What can a 500 watt-hour power station run?
Phones all weekend (about 25 charges), a CPAP for one to two nights without humidifier, LED lights for days, a laptop through a workday, and a car fridge for a day - but not a full-size refrigerator past half a day, and never a space heater, kettle or hair dryer, whose 1,000-plus watt draws exceed most 500 Wh units' inverters. It is the personal-electronics size, not the appliance size.
How long will a power station run a refrigerator?
A modern full-size fridge averages 50 to 100 running watts with compressor cycling - roughly 1,000 watt-hours a day. A 1,000 Wh unit therefore holds about one day of cold if you keep the door shut, and pairing with a 100-watt solar panel stretches it indefinitely in sun. An upright chest freezer holds cold longer than it runs, which is why freezers are the better outage bet.
Why do power stations never deliver their full rated capacity?
Two honest deratings: the inverter wastes 10 to 15 percent converting the battery's DC to wall-style AC, and most units reserve 10 to 20 percent at the bottom of the battery to protect its lifespan. Multiply those and 1,000 watt-hours on the label delivers about 700 to 800 to your devices - which is exactly why the calculator sizes to 80 percent of the load.
Is a power station better than a generator for outages?
For essentials, yes: silent indoors, no fuel runs, zero maintenance, and instant switchover - at 3 a.m. that is the whole game. For whole-house loads - HVAC, well pumps, electric ranges - generators win on watts per dollar and runtime without limit. The crossover sits near 2,000 Wh: below it the battery wins on every count except price per watt-hour, above it the generator's noise starts earning its keep.