TAKAGI TK-510U-E 2**

This site calculates the 209 therms figure; the registry does not publish it. The figure 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 0.81. The figure holds only at that test draw. A household that uses more or less hot water will use a different amount of gas. The source is DOE CCD, retrieved 2026-09-19. The full steps are on the page explaining how the annual cost is calculated.

The high draw pattern means a larger household, or one where showers and laundry overlap. This is the use the 209 therms figure was tested against. The registry lists the unit's maximum flow rate in gallons per minute as 5. The registry does not record how many fixtures a given home runs at once. So it cannot show whether that flow covers a particular household. Other gas tankless units at this draw pattern can be listed with the selector by fuel, space and size. Under the same test, the median unit in this class uses 182 therms a year. That is 27 therms less than this model.

For a reader checking yearly gas use, the main point is the rank. This model sits 323rd for lowest energy use of 397, in the highest quarter of its class. Most registered gas tankless units at the high draw pattern use less gas under the same test. This text does not state a running cost. The cost depends on your state's average residential gas price, and the page calculates it from your ZIP. To price the 209 therms at your own rate, use the cost calculator on your own ZIP. To compare against other models in the same class, find a same-class replacement by model number.