Every RV water heater gets a score from 0 to 100% built from three 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. Heaters are grouped as tank or tankless.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per gallon of tank, or per 1,000 BTU for tankless | 40% |
| Hot water output | gas recovery in gallons per hour for tanks, maximum flow in GPM for tankless | 35% |
| Warranty | warranty on the heater | 25% |
Where the numbers come from
BTU rating, tank size, recovery, flow, weight and warranty come from the maker’s manual or product page where one is published, and otherwise from the Amazon listing. Dometic’s manuals and Lippert’s Girard page are the main maker sources. The product page says where each number comes from. Prices are Amazon prices.
The factors
Value depends on the tier. For tank heaters it is the current price divided by the tank size, per gallon, on a log scale: $110 per gallon scores zero and $40 full marks. For tankless heaters it is the price per 1,000 BTU of input, on a log scale: $18 scores zero and $3 full marks.
Hot water output is gas recovery in gallons per hour for tank heaters (5 gallons per hour scores zero, 15 full marks) and the maximum rated flow in gallons per minute for tankless heaters (2.0 GPM scores zero, 3.9 GPM full marks).
Warranty is the limited warranty on the heater: 1 year scores zero and 3 years full marks.
What isn’t scored
Weight, amp draw, door size and ignition type are listed but not scored. Makers don’t publish them consistently. Efficiency isn’t scored because no maker publishes a tested figure, and BTU claims on budget tankless units are not independently measured.
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 seller that doesn’t publish one gets no warranty counted, so that factor scores zero and is marked estimated. Dometic does not publish a recovery rate, so its tank heaters get the neutral output score.
What isn’t ranked
Replacement tanks and cores, doors, parts and kits, 120 V electric-only heaters, portable camping heaters and home water heaters aren’t ranked.
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.