How long will a power station actually run your gear?

The number on the box — say, 1440 Wh — is not how long your device will run. To get actual runtime you have to account for two things the marketing spec sheet omits: usable capacity (most stations only let you draw 80–90% of rated capacity to protect the cells) and inverter overhead (the AC converter itself consumes 5–30W just to stay on, even before your device draws anything). Divide 1440 Wh by your 150W fridge and you get a naive 9.6 hours. Factor in 85% usable capacity, 85% inverter efficiency, and 15W of idle draw and you get closer to 6.5 hours — a 34% overstatement from the box math.

The CPAP example is particularly stark. A travel CPAP on its lowest pressure might draw only 30W, but the inverter overhead can equal or exceed the load itself. A unit with unverified idle draw might show a wide range like 8–22 hours rather than a single number — that spread is honest, not a bug. We show ranges instead of false precision when idle draw hasn't been independently measured.

Every estimate below comes from the same engine powering our product pages. When idle draw is unverified, we show a range using a conservative 5–30W overhead band. Hours above 100 are shown as “100+” because compounding estimation errors make single-decimal precision meaningless at long durations. We'd rather be honest about uncertainty than give you a precise-sounding number that's probably wrong.