ENVO WH-AZ01-180-NGI

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.81 for this unit. This site combined that value with the DOE test's daily hot-water draw for the high draw pattern. The result is 209 therms of natural gas a year, computed by this site and not published by the registry. The source is DOE CCD, retrieved 2026-09-19. The comparison group is the 397 models registered as a gas tankless unit at the high draw pattern. Within that group the median is 182 therms, and this unit is 27 therms above it. Its rank of 323rd lowest energy use of 397 places it in the highest quarter of its class for energy use.

The unit lists a maximum flow rate in gallons per minute of 4.3. That figure describes flow capacity, not energy use, and this page draws no conclusion from it. The 209 therms applies to a larger household, or one where showers and laundry overlap, because that is what the high draw pattern represents. A reader in that situation can use it as the test-based figure for this model. It is less useful for a household whose hot-water use differs from the federal test's daily draw. Actual gas use may then be higher or lower, and the data gives no estimate. To compare the position of 323rd of 397 with other units, use the selector by fuel, space and size. To look for a unit of the same class, you can find a same-class replacement by model number.

The running cost is not stated in the text. It depends on your state's average residential gas price, so the page computes it from your ZIP. The cost calculator on your own ZIP applies that price to the 209 therms for this model. The method behind the annual cost is described on its own page. The gap of 27 therms above the class median of 182 therms also converts to a yearly cost difference at that same price. This page does not state that amount. The installed price range is shown in its own block with its source and date. It is a modeled installed-cost range, not a quote, and it is not repeated here.