Mizudo FDG-CS90

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.84 for this unit. It also lists a maximum flow rate in gallons per minute of 2.3. The registry does not publish an annual energy figure. This site computed 91 therms from the registry's UEF and the DOE test's daily hot-water draw for the low draw pattern. The source is DOE CCD, retrieved 2026-09-19. The figure applies only at that test draw, so a household that draws more or less hot water will use a different amount. The data does not give figures for other draw patterns. The method is explained in how the annual cost is calculated.

This unit ranks 1st lowest for energy use among the 10 models registered as a gas tankless unit at the low draw pattern. That places it in the lowest quarter of its class. Its 91 therms is 2 therms below the class median of 93 therms. The figure suits a one- or two-person household whose hot-water use is close to the test draw. It does not describe a larger household, and the data has no figure for one. The data also does not say how many fixtures a flow of 2.3 gallons per minute can serve at once. For another fuel, space or size, use the water heater selector by fuel, space and size.

The running cost is not written here. It depends on your state average residential gas price, and no rate is available for this page. Use the cost calculator on your own ZIP to apply your rate to 91 therms. The result holds for the low draw pattern only. At one fixed rate, the 2 therms gap to the class median of 93 therms converts to a cost gap in direct proportion. The installed price range appears in its own block, with its source and date. It is a modeled installed-cost range, not a quote, and this text does not repeat its figures. To look for a same-class unit, you can find a replacement by model number.