Every transfer switch gets a score from 0 to 100% built from four factors, which 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. Switches are grouped by generator connection, 30 A and 50 A, and circuits have their own scale for each group.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per circuit | 35% |
| Circuits | circuits switched | 25% |
| Features | wattmeters, inlet box included, outdoor rated, UL listed | 20% |
| Warranty | warranty length | 20% |
Where the numbers come from
Circuits, ratings, what’s in the box, listings, warranty and the rest come from the maker’s product page, spec sheet or manual, or the maker’s own copy on its Amazon listing. Prices are checked at Amazon and the maker’s own store, and the lowest is used.
The factors
Value is the current price divided by the number of circuits, on a log scale, so going from $60 to $30 per circuit counts as much as going from $100 to $50. $100 per circuit scores zero and $25 full marks.
Circuits is the number of circuits it switches: for 30 A switches, 4 scores zero and 10 full marks; for 50 A switches, 6 scores zero and 16 full marks.
Features counts four things buyers otherwise pay for or need: wattmeters that show the generator’s load, a power inlet box in the kit, an outdoor rated enclosure, and a UL listing. Each is a quarter of the factor.
Warranty is the length of the consumer warranty: 1 year scores zero and 5 years full marks.
What isn’t scored
Manual or automatic switching, the largest generator rating, the inlet type, whether a cord is included, and weight are listed but not scored. Automatic switching is convenient but not better at its job, so it doesn’t earn points.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated.
Ties and discontinued models
Products are ranked by score within each group. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.