Methodology

Usable Wh, not box Wh

A power station's box rating is the energy stored in its battery. Inverter and conversion losses mean less reaches your appliances. We rank by price per usable Wh: the energy independent testers measured the unit delivering at its output.

Where each number comes from

We only publish a usable-Wh figure that a tester printed from their own discharge test, and every figure links to its source with the publisher, date and method. We do not estimate it, and we never use a manufacturer rating in its place. Our sources so far are OutdoorGearLab, Outdoor Life and StorageReview.

We skip a unit when its source contradicts itself or reports conflicting runs. If we find no credible measured figure for a model, we leave the model out.

Limits you should know

• Testers use different loads: about 80% of rated output (OutdoorGearLab), about 380 W (Outdoor Life), 350 W or an unstated load (StorageReview). Usable Wh is higher at heavier loads, so figures from different sources are not perfectly comparable.
• Results are for the unit the tester received and can change with firmware, temperature and battery age.
• Some tests are a year or more old. Each figure shows its source date.

Prices

Prices are checked by hand, not live. A price labeled "current" was read from a manufacturer's own store page on the date shown (latest check: November 13, 2026). Other prices are manufacturer list prices reported by the testers, and are labeled as such. Only in-stock prices we checked ourselves are used in "cheapest" claims. We do not display Amazon prices: where a product shows a "Check price on Amazon" link, Amazon's own page has the current price. Sale prices change quickly, so confirm before you buy.

Sizing

The size calculator and "best for" pages multiply typical appliance watts by hours, add 10% headroom and require the unit's rated output to cover everything running at once. Appliance wattages are our estimates, and startup surges (fridge compressors, pumps) are not modeled.

Independence

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