Every power station gets a score from 0 to 100% built from eight factors, and that score maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per watt-hour | 25% |
| Tested capacity | usable energy vs. rated | 15% |
| Battery life | chemistry, cycles, warranty | 15% |
| AC output | continuous watts | 15% |
| Charging speed | wall charge time | 10% |
| Portability | energy per kilogram | 10% |
| Solar input | watts vs. capacity | 5% |
| Features | UPS, expansion, USB-C, app | 5% |
Reference points by size
A 300 Wh camping station and a 5,000 Wh home battery aren’t judged by the same yardstick for price or output. These two factors use reference points set per size class; the rest are the same for every size.
| Size | Price per Wh scoring 0 → 100 | Continuous AC output scoring 0 → 100 |
|---|---|---|
| Small, under 500 Wh | $1.60 → $0.45 | 150 W → 800 W |
| Mid-size, 500-1,500 Wh | $1.10 → $0.35 | 500 W → 2,400 W |
| Large, 1,500-3,000 Wh | $0.95 → $0.30 | 1,500 W → 3,600 W |
| Home backup, 3,000 Wh+ | $0.95 → $0.30 | 2,400 W → 7,200 W |
Output is scored on a log scale, since going from 300 W to 600 W opens up far more appliances than going from 3,000 W to 3,300 W.
The factors
Value is the current lowest checked price divided by rated capacity. Prices are checked by hand and dated on every page; a product with no current price gets the neutral middle score.
Tested capacity is the share of rated watt-hours that independent reviewers actually got out of the AC outlets from a full charge. Every station loses energy in its inverter, so 80-90% is normal; 70% scores zero and 92% scores full marks. When several reviewers have tested a model, their results are averaged. Manufacturer claims don’t count here.
Battery life starts from chemistry: LiFePO4 (LFP) cells last several times longer than the NMC cells older and lighter stations use, and tolerate heat better. Rated cycles to 80% capacity (500 → 4,000) and warranty length (2 → 5 years) add the rest.
AC output is continuous inverter watts, scored against the size class reference points above. Surge and “boost” modes are listed in the specs but not scored, since they can’t run a load continuously. A DC-only unit, with no AC outlets at all, scores zero here.
Charging speed is the published time from empty to full on wall power: 4 hours scores zero, 50 minutes scores full marks.
Portability is watt-hours per kilogram, so a large station isn’t penalized for being heavy in absolute terms: 45 Wh/kg scores zero, 100 Wh/kg full marks.
Solar input is maximum solar watts relative to capacity: a station that can refill from solar in about an hour of peak sun scores full marks.
Features add up UPS (pass-through switchover) capability, expansion batteries, 100 W+ USB-C and an app.
Missing data
If a figure isn’t published or a model hasn’t been independently tested, that factor gets the neutral middle score (50) and the product page marks it as estimated. That keeps an untested product from looking worse than a tested one with average results, but also from looking better than one that tested well.
Ties and discontinued models
Products are ranked by score within each size. Discontinued models stay listed, since they’re still sold used and refurbished, but rank below every current model and can be hidden with the “Hide discontinued” filter.