How We Review: WilderWatt Method and Score Formula

We review products from their official specifications, not from physical testing. Every figure on WilderWatt comes from the manufacturer’s official listing on Amazon, checked on a specific date. We add our own math, such as runtime and solar charging estimates, and we always show the calculation.

Where does our data come from?

From the official Amazon product listings of each model, reviewed on the date shown on each page. We record every specification with the exact sentence it came from, so any figure can be traced back to its source.

If a listing does not publish a figure, we leave it blank. We do not fill gaps with estimates, forum posts or other markets’ data. When a spec is missing, we say so, because missing data is useful information too.

Do you test the products?

No, we do not run physical tests on the products we cover. We do not publish lab results, user testimonials or measurements we did not take.

What we do add is physics and electrical math. For example, we assume a power station delivers about 85% of its capacity after inverter losses. We also assume a portable panel delivers about 75% of its rating in real sun. These are general properties of the technology, not measurements of a specific model.

How is the WilderWatt score calculated?

Every product starts at 5 points and earns more only for what the manufacturer declares; the maximum is 10. A missing figure adds 0.

Power stations and kits:

LiFePO4 battery: +1.
Warranty of 5 years or more: +1 (3 years or more: +0.5).
Declared UPS function: +0.5.
Maximum solar input ÷ capacity of 0.5 or more: +1 (0.25 or more: +0.5).
AC output ÷ capacity of 1 or more: +1 (0.5 or more: +0.5).
Energy density of 90 Wh/kg or more: +0.5.
Kits only: included panel of at least 15% of the capacity, in W per Wh: +0.5.

Solar panels:

Efficiency of 23% or more: +1.5 (21% or more: +1).
Weight per 100 W of 2.5 kg or less: +1.5 (3.5 kg or less: +1; heavier: +0.5).
IP67 or IP68: +1 (IP65 or IP64: +0.5).
Bifacial: +0.5.
Warranty of 2 years or more: +0.5.

12 V LiFePO4 batteries:

LiFePO4 chemistry: +1.
Rated cycles of 6,000 or more: +1 (4,000 or more: +0.5).
BMS current in amps equal to or above the capacity in Ah: +0.5.
Bluetooth monitoring: +0.5.
Self-heating: +1 (low-temperature protection only: +0.5).
IP65 or higher: +0.5.
Warranty of 5 years or more: +0.5.
Energy density of 120 Wh/kg or more: +0.5.

Balcony solar kits (plug-in kits with a microinverter; we cover them only on our Spanish site, so no US page uses this formula):

Battery included: +1.
LiFePO4 battery: +0.5.
App or Wi-Fi monitoring: +0.5.
Bifacial panels: +0.5.
Inverter of 800 W or more: +0.5.
Warranty of 10 years or more: +1 (5 years or more: +0.5).
Expandable storage: +0.5.
IP65 or higher: +0.5.

Small wind turbines:

MPPT controller: +1.
Controller included: +0.5.
Start-up wind speed of 2.5 m/s or less: +0.5.
Warranty of 1 year or more: +0.5.
Implausible power claim: −2. This covers listings that promise many kilowatts from a small household turbine, which is not physically credible.

A wind turbine’s score is not comparable with a power station’s. It only measures what the listing declares within its own category, and it says nothing about how much energy the turbine will produce at your site. Our guide on whether small wind turbines are worth it covers that.

The score measures what the listing promises, not quality measured in a lab. Data was reviewed on September 26–27, 2026.

Can you show a worked example?

Yes. Here is a hypothetical station, not a real model. Imagine 1,000 Wh, LiFePO4, a 5-year warranty, a declared UPS, 400 W of solar input, 1,200 W of AC output and 12 kg.

Base: 5.
LiFePO4: +1. Warranty: +1. UPS: +0.5.
Solar ratio: 400 ÷ 1,000 = 0.4, so +0.5.
Output ratio: 1,200 ÷ 1,000 = 1.2, so +1.
Density: 1,000 ÷ 12 = 83 Wh/kg, below 90, so +0.

Total: 9.0 out of 10. Now take a hypothetical 100 W panel: 23% efficiency, 2.3 kg, IP65 and a 1-year warranty. It would score 5 + 1.5 + 1.5 + 0.5 = 8.5.

A hypothetical 12 V 100 Ah LiFePO4 battery with 4,000 cycles, a 100 A BMS, Bluetooth, low-temperature protection without self-heating, no published IP rating or warranty and 11 kg would score 5 + 1 + 0.5 + 0.5 + 0.5 + 0.5 = 8.0. Its density, 1,280 ÷ 11 ≈ 116 Wh/kg, falls just short of the 120 Wh/kg bonus.

How often do you update pages?

We review every page every 60–90 days, and sooner when a listing changes. Each page shows when it was published, updated and last reviewed.

When a specification changes, a product goes out of stock or a new version replaces it, we update the page and the score.

What do we not do?

We do not accept payment for rankings, positions or scores. Brands cannot buy a place on a list or a better score.

We also do not publish prices or Amazon star ratings, because they change constantly. We earn a commission through Amazon links, as explained in our affiliate disclosure. See about WilderWatt for who we are, or apply the method yourself with our guide on how to choose a portable power station.