Every microinverter gets a score from 0 to 100% built from five 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. Microinverters are grouped by panel count, one, two and four panels, on the same scales.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per watt of AC output | 25% |
| Grid listing | UL 1741 listing and rapid shutdown, which inspectors and utilities ask for | 20% |
| Efficiency | CEC weighted efficiency | 15% |
| Input current | DC current each input accepts, so big modern panels aren't clipped | 15% |
| Warranty | warranty length | 25% |
Where the numbers come from
Output, input current, efficiency, listings and warranty come from the maker’s data sheet, manual, warranty terms or product page. CEC weighted efficiency and UL 1741 SA and SB status are also checked against the California Energy Commission’s list of grid support inverters, and where the list and the data sheet differ the product page says so. Prices are checked at Amazon, the maker’s own store and solar retailers, and the lowest is used.
The factors
Value is the price of one unit divided by its maximum continuous AC output, on a log scale, so halving the price per watt always counts the same. $0.60 per watt scores zero and $0.15 full marks. When a listing sells several units together, the price is divided by the number of units first.
Grid listing is whether the inverter is listed to UL 1741, the safety and grid standard US utilities and inspectors ask for, and whether it meets NEC 690.12 rapid shutdown. A UL 1741 listing with rapid shutdown scores full marks, a UL 1741 listing where rapid shutdown isn’t stated scores 60%, and no UL 1741 listing scores zero.
Efficiency is the CEC weighted efficiency, which averages efficiency across the power levels an inverter sees through a day: 95% scores zero and 97.5% full marks.
Input current is the most DC current each panel input accepts. Modern 400 W and larger panels put out 13 to 15 A, and an input rated below that clips their output on bright days: 10 A scores zero and 18 A full marks.
Warranty is the maker’s standard warranty: 5 years scores zero and 25 years full marks. Where a warranty depends on registering the system, as Enphase’s 25 years does, the registered term is used and the product page says so. Optional paid extensions aren’t counted.
What isn’t scored
The largest panel the maker allows, the MPPT voltage range, peak efficiency, grid voltage, how it reports production, the enclosure rating and weight are listed but not scored.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated. There are two exceptions. A maker that doesn’t publish a warranty gets no warranty counted, so that factor scores zero, the same as the shortest warranty on the scale, and is marked estimated. And an inverter with no UL 1741 listing found scores zero for grid listing, since a utility may not approve it.
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.