A calculation, not an impression
Every rating shown on this site is a reproducible calculation, not an impression left after unboxing. This page documents the exact formula: the criteria used for each product family, their weight, and what happens when one of them could not be measured. Nothing here is rounded off for the occasion: the tables below are generated from the very same configuration file that computes the rating shown on every review.
Three rules, the same across the whole site
- The grid changes with the product family
Actual current delivered matters for a car battery booster; noise doesn't matter at all since it makes none. Noise tolerance matters for a power station you'll run indoors; it means nothing for a pocket power bank. Each family therefore has its own grid of criteria, with its own weights, listed further down. - An unmeasured criterion is never set to zero
If the measuring equipment or the protocol can't test a given criterion on a particular product, that criterion is simply absent from the calculation: never replaced with a zero, which would unfairly penalise the product, nor with an invented value. The weights of the criteria that were actually measured are then rescaled to total 100%, so the rating stays comparable with a product tested on every criterion. A worked example follows below. - The cost of energy is never fixed in place
When a review publishes a cost per kWh (or per 100 Wh depending on the family), that figure is not written once and for all into the article: it is recalculated on every page load from the current price on the product sheet and the actually measured capacity, never the manufacturer's claimed capacity. When the price drops, the figure shown drops with it, with nothing to edit by hand.
The grids, family by family
Weights as a percentage of the final rating, exactly as they are applied at the moment you read this page.
Power stations
| Criterion | Weight |
|---|---|
| Capacity and efficiency | 25 % |
| Delivered power | 25 % |
| Recharging | 15 % |
| Ports and control | 15 % |
| Build and endurance | 12 % |
| Noise | 8 % |
Balcony solar storage kits
The "Solar" category also covers two families judged differently: a balcony storage kit (battery and micro-inverter) is judged on usable capacity and app control, a standalone portable panel on portability and weather resistance. Efficiency and build quality are shared by both.
| Criterion | Weight |
|---|---|
| Capacity and expansion | 20 % |
| Solar input and MPPT | 20 % |
| Control and smart features | 15 % |
| Installation and compliance | 10 % |
| Efficiency | 25 % |
| Build and endurance | 10 % |
Portable solar panels
| Criterion | Weight |
|---|---|
| Portability and size | 25 % |
| Weather resistance | 20 % |
| Output ports | 20 % |
| Efficiency | 25 % |
| Build and endurance | 10 % |
Power banks
| Criterion | Weight |
|---|---|
| Capacity and runtime | 25 % |
| Output power | 20 % |
| Size and weight | 20 % |
| Ports and cables | 15 % |
| Recharging | 10 % |
| Build and endurance | 10 % |
Car battery boosters
| Criterion | Weight |
|---|---|
| Current actually delivered | 30 % |
| Cold-weather performance | 25 % |
| Capacity and versatility | 20 % |
| Safety and protections | 15 % |
| Build and endurance | 10 % |
12 V battery maintainers
The "Chargers" category covers two product families judged differently: a 12 V battery maintainer is judged on staying plugged in unattended for months, a mains or USB charger on the power it actually delivers port by port. Safety and build quality are shared by both.
| Criterion | Weight |
|---|---|
| Actual charging current | 30 % |
| Battery compatibility | 25 % |
| Cables and connectors | 10 % |
| Safety and protections | 20 % |
| Build and endurance | 15 % |
Mains and USB chargers
| Criterion | Weight |
|---|---|
| Actually delivered power | 25 % |
| Multi-port power sharing | 20 % |
| Protocol compatibility | 12 % |
| Size and technology | 8 % |
| Safety and protections | 20 % |
| Build and endurance | 15 % |
Generators
| Criterion | Weight |
|---|---|
| Actual available power | 20 % |
| Runtime and fuel consumption | 20 % |
| Noise | 20 % |
| Power quality and reliability | 15 % |
| Portability | 10 % |
| Build and endurance | 15 % |
A real example, not a demonstration
Take a review actually published on this site: Aferiy P210: our full review. Its "noise" criterion, worth 8% for power stations, could not be measured (no decibel reading was recorded during testing). The other five criteria add up to 92% on their own, so they are rescaled to represent 100% of the calculation, each keeping the same proportion relative to the others.
| Criterion | Nominal weight | Weight actually applied | Rating |
|---|---|---|---|
| Capacity and efficiency | 25 % | 27.2 % | 4.0 / 5 |
| Delivered power | 25 % | 27.2 % | 4.3 / 5 |
| Recharging | 15 % | 16.3 % | 4.3 / 5 |
| Ports and control | 15 % | 16.3 % | 4.1 / 5 |
| Build and endurance | 12 % | 13 % | 3.9 / 5 |
| Noise | 8 % | 0 % | absent, not counted |
Rating shown on the review: 4.1 / 5. That is exactly the figure the calculation above produces, to one decimal place: no editorial rounding behind the scenes.
The noise criterion, still a work in progress
Operating noise is a criterion buyers expect on this kind of equipment. We measure it whenever the equipment allows it: as of today, 25 of the 51 power station and generator reviews publish a reading. The others state honestly that it wasn't measured rather than inventing a figure, following the second rule above.
Frequently asked questions
It doesn't change on its own: if a criterion missing at test time is measured later (a decibel reading, for instance), the review is updated and the rating recalculated with that extra criterion included. That's the only way a rating moves outside of a newly tested product revision.
No, deliberately so: what makes a good power station (capacity, sustained power) isn't what makes a good car battery charger (cold tolerance, safety). Each grid listed above was built for its own product family.
Always: it's recalculated on every page load from the current price on the product sheet and the measured capacity published in the review, never stored as a fixed figure. If the price changes, the figure shown changes with it.
Our team, who has been testing the products in this catalogue for over ten years. Every full review states the conditions under which the measurements were taken.