THERMALUX NR662-OD-NG

The figure of 135 therms rests on the 0.82 UEF, the ratio of hot water delivered to energy used. This site computes the result from the registry's UEF and the DOE test's daily hot-water draw for the medium pattern. The registry itself does not publish the yearly result. The source is DOE CCD, retrieved 2026-09-19. The condition matters: 135 therms applies only at the medium draw pattern and only for natural gas. A household that draws more or less hot water than the test assumes will use a different amount. The maximum flow rate in gallons per minute is 3.6 for this model, and it does not enter the energy calculation.

Among the 80 models registered as a gas tankless unit at the medium draw pattern, this unit ranks 32nd lowest in energy use. That places it in the second-lowest quarter of its class. Its 135 therms equals the class median of 135 therms, so the difference is 0 therms. This suits a reader confirming that a unit sits at the class median. It does not suit a reader who needs the lowest use in the class, because other models in the comparison use less. The comparison covers only the same heater type and draw pattern. It says nothing about storage tank or electric models.

The running cost is not stated here because it depends on your state's average residential gas price. This page does not estimate it, and no rate for your home is available to it. Multiply 135 therms by your own rate, or use the cost calculator for your ZIP to do it. Read how the annual cost is calculated to check the arithmetic. The modeled installed-cost range appears in its own block on this page, with its source and date. It is a modeled range, not a quote. To compare against a same-class unit, find a replacement by model number. That comparison keeps the medium draw pattern and the gas tankless type.