Mizudo FDG-CS100

The registry lists this unit at a UEF, the ratio of hot water delivered to energy used, of 0.81. The annual figure is not from the registry. This site computed 95 therms of natural gas from that UEF and the DOE test's daily hot-water draw. That draw belongs to the low draw pattern, a one- or two-person household. The number holds only at that draw. A household that uses more or less hot water will use a different amount of gas, and this page does not estimate it. The source is the DOE CCD, retrieved 2026-09-19.

Among the 10 models registered as a gas tankless unit at the low draw pattern, this one ranks 7th lowest for energy use. Its 95 therms is 2 therms above the class median of 93 therms. That puts it in the second-highest quarter of its class. The registry also gives a maximum flow rate in gallons per minute of 2.5. The energy figure fits a one- or two-person household that heats water with natural gas. It does not describe a larger household, or a unit on another fuel. To look for a unit in the same class, use the same-class replacement finder. To filter by fuel, space and size, use the water heater selector.

Running cost is not stated here because it depends on your state's average residential gas price. Multiply 95 therms by that price per therm to get a yearly figure at the low draw pattern. The cost calculator does this from your ZIP. The calculation method explains the steps. Multiply 2 therms by the same price to see the yearly cost of the gap above the median. The class median is 93 therms at the test draw. The installed price range appears in its own block on this page, with its source and date.