JOHN WOOD GCF-40 1**

The 173 therms figure is a site calculation, not a registry value. It starts from the registry's UEF, the ratio of hot water delivered to energy used, which is 0.64 for this model. That UEF is applied to the federal test's daily hot-water draw for the medium draw pattern. The source is DOE CCD, retrieved 2026-09-19. Among the 288 gas tank models at this draw pattern, this one ranks 44th lowest for energy use. That places it in the lowest quarter of its class. The gap to the median of 185 therms is 12 therms. The steps are set out in how the annual cost is calculated.

This model fits a household that matches the medium draw pattern, a typical three- or four-person household on a busy morning. Its first hour rating, the gallons of hot water available in the first hour from a full tank, is 70 gallons. The rated volume is 38 gallons. The registry data does not show whether those figures cover your own peak hour. The energy figure holds only at the federal test's daily draw. A household that draws more hot water than that test would use more than 173 therms. The water heater selector filters by fuel, space and size.

This page does not state a running cost. The cost depends on the state average residential gas price, and no rate for your location is given here. The cost calculator applies the rate for your ZIP to 173 therms. The figure covers natural gas only, so a home without a gas supply falls outside it. The gap of 12 therms below the 185 therms median is a difference in energy, not in cost. To compare against another unit in the same class, find a same-class replacement by model number. The installed price range appears in its own block on this page.