Every landscape lighting transformer 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. Transformers are grouped by rated output, up to 150 W, 200 to 300 W and 600 W and up, and use the same scale in every group.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per 100 W of rated output | 25% |
| Voltage taps | highest output voltage and number of taps, for long cable runs | 20% |
| Controls | photocell, timer, app control and independent zones included | 20% |
| Build | stainless steel or metal enclosure, toroidal core and circuit breaker | 15% |
| Warranty | warranty length; lifetime scores full marks | 20% |
Where the numbers come from
Ratings, output voltages, controls, build and warranty come from the maker’s product pages, spec sheets and warranty terms, or the maker’s own copy on a retail listing. Prices are checked at Amazon, and the lowest price at a store the page links to is used.
The factors
Value is the current price divided by the rated output, in dollars per 100 W, on a log scale, so halving the price always counts the same. $150 per 100 W scores zero and $20 per 100 W full marks.
Voltage taps rewards a transformer that can make up for voltage drop on long cable runs. 60% of it is the highest output voltage, with 12 V scoring zero and 15 V full marks. The other 40% is the number of distinct output voltages, with one scoring zero and four full marks. Two terminals at the same voltage count as one. When a maker gives a range of output voltages but not the steps in between, the count part scores the neutral middle and the factor is marked estimated.
Controls is 25% each for a photocell included or built in, a timer included or built in, app control over Wi-Fi, and two or more zones that switch on their own schedules. A timer or photocell sold separately doesn’t count.
Build is 50% for a stainless steel case (30% for other metal or painted steel, nothing for plastic), 30% for a toroidal core, which runs cooler and quieter than the common laminated core, and 20% for a built-in circuit breaker or resettable overload cutout.
Warranty is the maker’s warranty: 1 year scores zero and 10 years full marks, and a lifetime warranty scores full marks. Where a maker covers the electronics for fewer years than the case and core, the electronics term is used.
What isn’t scored
Terminal type, cord length, weight, whether the output is AC or DC, and release date are listed but not scored. The rated wattage sets the group and the price per 100 W, but isn’t scored on its own.
Missing data
Warranty is the factor that most separates a contractor transformer from a budget one, so a maker that doesn’t publish one gets no warranty counted: that factor scores zero, the same as a one-year warranty, and is marked estimated. If the output voltages aren’t published, the taps factor gets the neutral middle score (50) and is marked estimated. Controls and build score neutral only when none of their parts is published; a feature the maker doesn’t mention otherwise counts as absent.
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.