Rinnai manufactures 13 models of tankless water heaters than have received Energy Star certification, with models receiving energy factor ratings ranging from 0.82 to 0.96. The minimum rating for certification is 0.82. Rinnai's models meet the Energy Star standard of using 40 percent less energy than standard water heaters.
The energy factor is an efficiency rating that represents the ratio of useful energy output from a water heater in relation to the total energy delivered to the heater.
To receive Energy Star certification, tankless water heaters must also deliver at least 2.5 gallons of hot water per minute and be sold with at least a 10-year warranty on the heat exchanger and a five-year warranty on parts.