FRIEDRICH RTGH-S10I

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.96 for the FRIEDRICH RTGH-S10I. This site, not the registry, computed 176 therms of natural gas a year from that UEF and the DOE test's daily hot-water draw for the high draw pattern. The source is DOE CCD, retrieved 2026-09-19. Among the 397 models registered as a gas tankless unit at this draw pattern, the unit is 12th lowest in energy use of 397, which places it in the lowest quarter of its class. Its figure sits 6 therms below the class median of 182 therms. That comparison holds only at the test's draw. The data does not show how much hot water any particular home uses.

The high draw pattern describes a larger household, or one where showers and laundry overlap. The 176 therms figure fits a reader whose home matches that description and who wants to compare units within the same class. It does not describe a home with a lower draw pattern, and this page has no energy figure for other draw patterns of this model. The maximum flow rate in gallons per minute is 5.2. The temperature rise at which that flow is rated is not available in this data, so it cannot be set against a home's incoming water temperature here. To narrow options by fuel, space and size, use the water heater selector. To match an existing unit, find a same-class replacement by model number.

Running cost is not written in the text because it depends on your state's average residential gas price. The page computes it from your ZIP, and no cost figure is estimated here. The gap of 6 therms against the class median of 182 therms is a difference in energy, so what it means in cost depends on that same price. The cost calculator applies your rate to 176 therms, and the methodology page explains how the annual cost is calculated. Both figures are for natural gas at the high draw pattern. The modeled installed-cost range appears in its own block with its source and date. It is a modeled range, not a quote, and it is not repeated in this text.