We independently review everything we recommend. When you buy through our links, we may earn a commission. Learn more›

How We Review

This page explains how GadgetsDiary researches and rates products. Our ratings come from research, not from running battery or charging tests on products.

Step 1: Define the need

We start from what a shopper is trying to solve, such as keeping a laptop running on a flight, powering a CPAP on a camping trip, or charging several devices from one wall outlet, and set the criteria that matter for that need before looking at products.

Step 2: Gather information

We use manufacturer specifications, product listings, published capacity, output and port ratings, and recurring themes in buyer feedback. We attribute buyer feedback as feedback and do not present it as our own measurement.

Step 3: Compare against the criteria

Criteria depend on the category. Common ones are:

  • Power banks: listed capacity, output per port and combined output, port types, size and weight, recharge input, and value.
  • Portable power stations: listed capacity and continuous output, number and type of outlets and ports, recharge options, weight, and value.
  • Solar chargers and generators: listed panel wattage, compatible power stations or devices, folded size and weight, weather rating where stated, and value.
  • Wall, car and wireless chargers: listed output and combined output, port types, supported charging standards where stated, size, and value.
  • Cables, hubs and adapters: listed data and power ratings, length, ports and supported display output where stated, build, and value.

The GadgetsDiary Score

The GadgetsDiary Score is calculated the same way for every product. We start from the average Amazon buyer rating and adjust it for how many ratings the product has, so a product with only a few ratings is pulled toward a typical rating until it has enough ratings to stand on its own:

Adjusted rating = (average rating × number of ratings + 4.2 × 500) ÷ (number of ratings + 500)

The adjusted rating is then placed on our 10-point scale, where an adjusted 3.0 out of 5 equals 6.2 and an adjusted 5.0 equals 9.4. This is why a product rated 4.8 by 25 buyers can rank below one rated 4.5 by 3,000 buyers.

The criteria above decide which products make a list and which use each one is best for. The score decides the order. The score is a research based rating, not a laboratory result, and affiliate commissions play no part in it.

Limits of our method

Specifications and listings can be wrong or change. Capacity, output, runtime and compatibility details are stated by manufacturers under their own conditions, which may differ from your use. Always check the manufacturer details for the exact model you plan to buy, especially output ratings, supported devices, and charging and airline rules.

How products are chosen

We select products that fit the need, have enough reliable information to compare, and reflect a range of brands. We do not pad a list with weak products to reach a round number.