ARISTON GN40T2-3-*

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.6 for this model. This site computed 185 therms a year from that UEF and the DOE test's daily hot-water draw for the medium draw pattern. The registry does not publish the annual figure itself. The model ranks 89th lowest energy use of 288, in the second-lowest quarter of its class, and its difference from the class median of 185 therms is 0 therms. The source is DOE CCD, retrieved 2026-09-19. The method behind the annual cost explains the calculation step by step.

The 185 therms figure applies only to the medium draw pattern. The registry lists a first hour rating, the gallons of hot water available in the first hour from a full tank, of 73 gallons for this model, with a rated volume of 38 gallons. A household whose hot-water use differs from the medium draw pattern should expect energy use different from 185 therms. This page has no figures for other draw patterns, so it cannot say by how much. To compare sizes and fuels against your own space, the water heater selector filters by fuel, space and size.

The running cost is not written here because it depends on the average residential gas price in your state. The cost calculator applies that price, found from your ZIP, to the 185 therms figure for this model. Because the model sits at 0 therms from the class median of 185 therms, a typical model in the same class would use the same energy at the medium draw pattern. The modeled installed-cost range is shown in its own block with its source and date. It is a modeled range, not a quote. To check a same-class alternative, find a replacement by model number.