Original research · published 2026-07-31
The Capacity Gap Report
Every power station prints a watt-hour number on the box. Almost none of them tell you how much of it reaches your appliance — and after auditing 80 models, we found the industry cannot tell you either.
Nobody measures this the same way, so nobody can tell you the number
We set out to publish a simple figure: across the catalogue, what share of rated capacity actually reaches a load? We could not. Of 80 models, 21 carry any published capacity measurement at all. Of those, 9 turned out to be rated capacity multiplied by an assumed efficiency, or a figure the source itself flagged as informal. That leaves 12 real measurements — 11 of them on AC — from 3 outlets, and only 3 of the 12 published the load they tested at.
Among the AC measurements the delivered share runs from 75.5% (Anker SOLIX C800 X) to 97.7% (Bluetti Elite 100 v2) — a spread of 22 percentage points. That spread is not a ranking of manufacturer honesty. A battery worked harder gives back less, and the lowest figure here was taken at 1200 W — the heaviest load anyone in this set published. The highest did not state a load at all, which is the more common case: the only test loads published anywhere in this dataset are 50 W, 60 W, 1200 W. So we cannot tell you whether the 22-point spread reflects the hardware or the test bench, and neither can anyone else.
Which is where “you get about 85%” comes from. It is repeated across manufacturer blogs as though it were a measurement. It is a plausible midpoint of numbers that were never comparable — and against the measurements that do exist it lands nine points high at one end of the range and thirteen points low at the other.
The 11 AC measurements we could verify
Delivered energy through the inverter, against the manufacturer’s rating. Where a source published a range, the range is shown — narrowing it would be inventing precision.
| Model | Rated | Delivered | Share of rated | Test load | Source |
|---|---|---|---|---|---|
| Jackery Explorer 300 Plus Discharged at a 50 W load — among the lightest test conditions in this set. | 288 Wh | 253 Wh | 87.8% | 50 W | Trusted Reviews |
| Jackery Explorer 2000 v2 | 2,042 Wh | 1,710 Wh – 1,740 Wh | 83.7% – 85.2% | not published | OutdoorGearLab |
| EcoFlow DELTA 2 Drawn from a six-month ownership test rather than a single bench run. | 1,024 Wh | 890 Wh – 900 Wh | 86.9% – 87.9% | not published | Portable Power Lab |
| EcoFlow DELTA Pro 3 | 4,096 Wh | 3,790 Wh | 92.5% | not published | OutdoorGearLab |
| Bluetti AC180 | 1,152 Wh | 950 Wh | 82.5% | not published | OutdoorGearLab |
| Bluetti AC200L The source reports the spread as load-dependent, which is the whole problem in one row. | 2,048 Wh | 1,770 Wh – 1,900 Wh | 86.4% – 92.8% | not published | Trusted Reviews |
| Bluetti Elite 100 v2 | 1,024 Wh | 1,000 Wh | 97.7% | not published | Trusted Reviews |
| Bluetti Apex 300 | 2,765 Wh | 2,550 Wh – 2,580 Wh | 92.2% – 93.3% | not published | Trusted Reviews |
| Anker SOLIX C800 X Extracted over 29 minutes at 1200 W — the heaviest load in this set, and the lowest share. | 768 Wh | 580 Wh | 75.5% | 1200 W | Trusted Reviews |
| Anker SOLIX C1000 | 1,056 Wh | 860 Wh | 81.4% | not published | OutdoorGearLab |
| Anker SOLIX C2000 Gen 2 Published as a percentage (~86% on AC); the Wh figure here is that share of rated. | 2,048 Wh | 1,761 Wh | 86.0% | not published | Trusted Reviews |
Measured on DC, and why it sits in its own table
A USB or 12 V figure never passes through the inverter, so it skips the single largest loss in the chain. Putting it in the table above would flatter the unit and mislead you.
| Model | Rated | Delivered | Share of rated | Test load | Source |
|---|---|---|---|---|---|
| Anker SOLIX C300 Measured over USB at 60 W. This never passes through the inverter, so it is not comparable to the AC rows. | 288 Wh | 269 Wh | 93.4% | 60 W | Trusted Reviews |
The 9 claims we threw out, and why
These are shown rather than dropped, because the reason each one fails is the substance of this report. Most of them are the 85% rule of thumb wearing a measurement’s clothes.
- Jackery Explorer 1000 Plus
~1074 Wh usable at ~85% (Backup Power Hub)
Rated capacity multiplied by an assumed 85% efficiency. That is the rule of thumb, not a test of it.
- Jackery Explorer 2000 Plus
~1736 Wh calc at 85% (Backup Power Hub, computed not bench-measured)
The source states outright that the figure is computed rather than measured.
- EcoFlow DELTA 3
~870 Wh effective at ~85% (Backup Power Hub, calculated)
Calculated from rated capacity at an assumed efficiency.
- EcoFlow DELTA 3 Plus
~870 Wh effective at ~85% (est., same cells as DELTA 3)
Estimated by analogy to a different model. No measurement of this unit exists.
- Bluetti AC240
~1,300-1,679 Wh (StorageReview / Trusted Reviews)
The upper bound exceeds the 1,536 Wh rating once conversion losses are accounted for, so the two sources are not measuring the same thing.
- Bluetti Elite 200 v2
~2,074 Wh full-rated delivered (Trusted Reviews)
Equal to the 2,073.6 Wh rating. AC conversion cannot be lossless, so this restates the spec.
- Anker SOLIX F2000
Delivered <half rated capacity under very light load — full-load figure not published
No specific figure, and a result that surprising needs a protocol we can read before it means anything.
- Pecron E1000LFP
~600-700 Wh used in an 8-hr laptop+CPAP+router test with >30% left
A field test that never ran the pack down, so it bounds the capacity rather than measuring it.
- VTOMAN FlashSpeed 1000
~700-750 Wh usable estimated after AC conversion loss (Battery Skills, informal)
Recorded by its own source as an informal estimate.
What this report cannot tell you
We own no hardware and ran none of these tests. Every figure above was measured by someone else and is credited to them; our contribution is the audit, the exclusions, and the refusal to average numbers that are not comparable. 59 of the 80 models in our catalogue have no published capacity measurement of any kind, and for those we can tell you nothing — which is why no capacity-derived figure appears in the BatteryRank score.
If you test power stations and publish your load conditions, we would rather cite you than estimate. The gap this report documents closes one published protocol at a time.
Where the numbers live
- The full data table — every model, every sourced field, with dates.
- How the score is computed — and why delivered capacity is reported rather than scored.
- The rankings — computed from sourced specs, with the formula published.