Rheem RTGH-S11I

The registry does not list the 176 therms figure. This site calculated it from two inputs. The first is the registry's UEF, the ratio of hot water delivered to energy used, which is 0.96 for this model. The second is the daily hot-water draw in the DOE test for the high draw pattern. The registry data comes from DOE's Compliance Certification Database, retrieved 2026-09-19. The 176 therms figure applies only at the federal test's daily draw. A household that uses more hot water than that test will use more gas than 176 therms. A household that uses less will use less gas. The steps from this energy figure to a yearly cost are set out in how the annual cost is calculated.

The high draw pattern stands for a larger household, or one where showers and laundry overlap. The registry lists this unit's maximum flow rate in gallons per minute as 5.8. Among the 397 gas tankless models registered at the high draw pattern, it ranks 12th lowest for energy use. That rank puts it in the lowest quarter of its class. The registry gives no figure for households whose daily use falls well below the test's draw. How this unit compares with other models in such homes is unknown. The energy figure is for natural gas only. To compare this model with others in the same class, use the same-class replacement search by model number.

The text on this page does not state a running cost. The cost of 176 therms of natural gas depends on your state's average residential gas price. For that reason, the page calculates the cost from your ZIP. Readers in different states will see different costs for the same 176 therms. The gap to the class median follows the same rule: what it is worth in money depends on your own rate. The installed price range appears in its own block, with its source and date. It is a modeled installed-cost range, not a quote. To see the yearly cost at your own rate, enter your ZIP in the water heater cost calculator for your ZIP.