Every cold plunge chiller 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. Chillers are grouped by compressor size, up to 1/2 HP and over.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per horsepower of compressor | 30% |
| Coldest | lowest water temperature it holds | 15% |
| Sanitation | filter and ozone or UV sanitizer included | 10% |
| Heating | heats as well as cools | 10% |
| Noise | rated sound level | 10% |
| Warranty | warranty on the chiller | 25% |
Where the numbers come from
Compressor size, temperature range, filter and sanitizer, noise and warranty come from the maker’s spec sheet, manual or product page. 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 compressor size in horsepower, on a log scale, so going from $6,000 to $3,000 per HP counts as much as going from $3,000 to $1,500. $6,000 per HP scores zero and $500 full marks. Few makers publish a cooling capacity in Btu, but all name the compressor size; the Btu rating is listed when there is one.
Coldest is the lowest water temperature the maker says it holds: 45 °F scores zero and 37 °F full marks.
Sanitation is half for a filter in the box and half for a sanitizer: ozone and UV together score full marks for that half, and either one alone 70.
Heating scores full marks when the chiller heats as well as cools, and zero when it only cools.
Noise is the maker’s sound rating: 65 dBA scores zero and 45 dBA full marks.
Warranty is the warranty on the chiller: 1 year scores zero and 3 years full marks.
What isn’t scored
Cooling capacity, largest tub, pump flow, refrigerant, voltage and app control are listed but not scored. Independent cool-down and noise tests are shown on the product page when there are any.
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.