TAKAGI TK-110U-I 2**

The figure of 137 therms is computed by this site, not published by the registry. It combines the registry's UEF, the ratio of hot water delivered to energy used, of 0.81 with the daily hot-water draw that the DOE test assigns to the medium draw pattern. That pattern describes a typical household on a busy morning. The fuel is natural gas, and the source is the DOE CCD, retrieved 2026-09-19. The figure holds only under those conditions. A household that draws more or less hot water than the test assumes will use a different amount, and this page has no measured value for that case. The steps are listed in the methodology for water heater annual cost.

Within its class, this unit sits at 52nd lowest energy use of 80 gas tankless models at the medium draw pattern. That places it in the second-highest quarter of the class for energy use, 2 therms above the class median of 135 therms. The rank describes energy use at the test draw only. It says nothing about delivery beyond the maximum flow rate in gallons per minute, listed at 3.5. The figure suits a household whose hot-water use resembles the medium draw pattern and who is comparing like with like. It suits less a household whose use is far from that pattern, or one comparing against another fuel or heater type. For a same-class alternative, try the replacement finder by model number or the selector by fuel, space and size.

Running cost is not stated here because it depends on the natural gas price you pay, and the state average residential gas price differs by state. Multiplying 137 therms by your own rate gives the yearly gas cost at the medium draw pattern. The cost calculator on your own ZIP does this with your state average. The result is a modeled cost, not a bill. Actual gas use, local rates and the test conditions behind the 0.81 UEF can all differ from your home. The installed-cost range on this page is a separate modeled block with its own source and date, and it is not repeated here.