How We Rank Power Stations

Value, output and portability are normalized within each size class, because they scale with capacity; recharge rate and features are normalized across the whole catalog, with the top and bottom 5% clipped so one outlier cannot distort the scale.

The ratings and their weights

Rating	Weight	What it measures	Why it matters
Value	25%	Rated watt-hours per dollar at current street price, compared within the size class	The single biggest driver of whether a unit is worth buying. We show the inverse ($ per kWh) on every page.
Power output	15%	Continuous AC watts divided by capacity, capped at 2.5 W/Wh, compared within the size class	A 1kWh unit with a 1800W inverter can run tools and appliances a 500W inverter cannot.
Battery longevity	15%	LiFePO4 scores 1.0; NMC scores 0.25. Cycle rating adjusts within chemistry.	LiFePO4 typically lasts 3,000 to 6,000 cycles versus 500 to 800 for NMC, and is more thermally stable.
Recharge speed	15%	Max AC input watts divided by capacity (C-rate), capped at 1.5	A unit you can refill in an hour during a brief outage is far more useful than one that needs eight.
Portability	10%	Watt-hours per pound, compared within the size class	Energy density. A unit that is heavy for its size is harder to move and usually older.
Features	10%	Points for UPS switchover of 20 ms or less (2), app (1), expandable (1), 240V (1), USB-C of 100W or more (1), solar input of 400W or more (1), wireless pad (0.5)	Small weight on purpose. Features matter, but not as much as the battery and inverter.
Tested capacity	10%	Independently measured usable capacity as a percent of rated Wh (median across sources)	Rated Wh is a marketing number. Delivered Wh is the truth. When no independent test exists, the product receives the median score of the tested ones for this rating, so a missing test neither rewards nor penalizes it; the model page says when that applies.

Why rankings are shown within size classes

Cross-class comparisons are rarely what a buyer needs, so every page ranks within one of these:

Small (under 500 Wh) — Phones, laptops, CPAP overnight, camera batteries. Carry-on friendly.
Medium (500–1,499 Wh) — Weekend camping, mini-fridge, power tools, short outages.
Large (1,500–2,999 Wh) — Multi-day outages, full-size fridge, RV and van life.
Extra Large (3,000 Wh and up) — Whole-home backup, 240V, expandable systems.

Where the data comes from

Specifications come from manufacturer spec sheets. Prices are approximate street prices and are refreshed periodically; the retailer price at checkout is what applies. Measurements come from the reviewers and labs we track: for each we store the number, the unit, the source and a link, and never copy a reviewer's text. Where a source is paywalled, we record only that a test exists. See the reviewers and labs we track.

What we don't do

We don't accept payment, sponsorship or free products for placement.
We don't adjust scores by hand. If a ranking looks wrong, the fix is a data correction or a formula change, and formula changes are noted on the updates page.
We don't rank power stations we can't find a spec sheet and a current price for.
We don't copy reviewers' text. We record their numbers and link to their work.

How the site makes money

Links to retailers are affiliate links and may earn us a commission at no cost to you. We link to every ranked power station the same way, so there is no incentive to favor one over another. More in About.

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