Ruud RTGH-S10I

The 176 therms figure is calculated by this site. The registry does not publish it. It combines the registry's UEF, the ratio of hot water delivered to energy used, with the DOE test's daily hot-water draw for the high draw pattern. This model's UEF is 0.96. The registry values come from the DOE CCD and were retrieved on 2026-09-19. The result applies only at the federal test's daily draw. This page has no energy figure for a household that uses more or less hot water than the test assumes. The steps behind the number are set out in how the annual cost is calculated. If a document you are checking lists a UEF other than 0.96 for RTGH-S10I, this page uses the registry record as its reference.

The high draw pattern stands for a larger household, or one where showers and laundry overlap. Both the 176 therms figure and the class comparison assume that level of use. The registry also lists a maximum flow rate in gallons per minute of 5.2 for this unit. The data does not say whether 5.2 is enough for the fixtures a particular home runs at once. A smaller household may fall under a different draw pattern. In that case, this model's class rank does not apply, and this page has no energy figure for that pattern. To match a unit by fuel, available space and size, see the selector by fuel, space and size.

The 6 therms gap to the class median, noted above, is measured in therms of natural gas, not in money. What that gap is worth depends on your state's average residential gas price. For that reason, the page calculates running cost from your ZIP instead of stating it here. You can get that figure from the cost calculator for your own ZIP. The installed-cost range shown elsewhere on the page is a modeled range, not a quote. The comparison group of 397 includes only models registered as gas tankless units at the high draw pattern. Other heater types and other draw patterns are not part of it. To look at models in the same class, use find a same-class replacement by model number.