Every UPS gets a score from 0 to 100% built from six 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. Units are grouped as desktop (under 1,000 VA), tower (1,000 to 2,000 VA), and rackmount and online, and use the same scale in every group.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per 100 W of rated real output | 25% |
| Output | rated real power in watts | 15% |
| Topology and waveform | standby, line-interactive or online, and sine or simulated sine on battery | 20% |
| Runtime | maker-stated runtime at a 100 W load | 10% |
| Features | AVR, LCD, USB charging, management and a lithium battery | 15% |
| Warranty | warranty length and connected-equipment guarantee | 15% |
Where the numbers come from
VA and watt ratings, topology, waveform, outlets, features, runtime and warranty come from the maker’s product copy, including the maker’s own copy on a retail listing. A UPS that is sold with automatic voltage regulation (AVR) and makes no double-conversion claim is recorded as line-interactive, since AVR is a line-interactive feature. A figure the listing does not give is left blank, never guessed. 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 real power, in dollars per 100 W, on a log scale, so halving the price always counts the same. $120 per 100 W scores zero and $15 per 100 W full marks.
Output is the rated real power in watts: 250 W scores zero and 1,800 W full marks. Watts, not VA, is the real limit on what a UPS can carry.
Topology and waveform is worth half topology and half waveform. For topology, standby scores 0, line-interactive 60% and online double-conversion 100%. For waveform, a simulated, stepped or PWM sine wave on battery scores 0 and a sine wave 100%. If only one of the two is published, the other half takes the neutral score and the product page marks the factor as estimated.
Runtime is the maker-stated runtime at a 100 W load: 10 minutes scores zero and 75 minutes full marks. Half-load and full-load runtimes, where published, are shown on the product page but not scored, because makers do not publish the same points.
Features is 25% for AVR, 20% for an LCD, 15% for front USB charging ports, 20% for a data port, management software or a network-card option, and 20% for a lithium battery. A feature the listing does not mention counts as absent.
Warranty is 70% warranty length and 30% connected-equipment guarantee. For length, 1 year scores zero and 5 years full marks. For the guarantee, $50,000 scores zero and $500,000 full marks on a log scale; a guarantee the listing does not state counts as zero.
What isn’t scored
Battery energy, whether the battery is user-replaceable, outlet counts, format (desktop, tower or rack), half-load and full-load runtime, and release date 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. The exception is warranty: a maker that doesn’t publish one gets no warranty counted, so that factor scores zero, the same as a one-year warranty with no guarantee, and is marked 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.