AMERICAN T-H3-OS-N 1**

The 178 therms figure is computed by this site, not published by the registry. It starts from the registry's UEF, the ratio of hot water delivered to energy used, listed as 0.95 for this model. The DOE test's daily hot-water draw for the high draw pattern is then applied. The source record is the DOE CCD, retrieved 2026-09-19. The figure applies to natural gas at that federal test draw only. Actual use in a home depends on real hot-water demand, which the registry does not record. The methodology page explains how the annual cost is calculated from this energy figure.

This unit is compared with the 397 models registered as a gas tankless unit at the high draw pattern. Its use is 4 therms below the class median of 182 therms, and its rank of 45th lowest places it in the lowest quarter of its class for energy use. Its maximum flow rate in gallons per minute is 5.8. The high draw pattern describes a larger household, or one where showers and laundry overlap, so the figure fits that kind of use. It does not describe a household with a lighter draw. Energy use for other draw patterns is not available on this page, so it is not estimated here.

The running cost is not written in this text because it depends on your state's average residential gas price, which is not part of the registry record. To see it, enter your ZIP in the cost calculator, which applies your rate to the 178 therms at the high draw pattern. If your household uses hot water differently from that pattern, the result will differ, and this page has no figure for that case. The modeled installed-cost range is shown in its own block with its source and date. It is a modeled range, not a quote, and it is not repeated here. To look for a unit in the same class, use the replacement finder by model number with T-H3-OS-N 1**.