Mizudo HS180

The figure of 206 therms comes from this site's own calculation, not from the registry. The inputs are the registry's UEF, the ratio of hot water delivered to energy used, and the DOE test's daily hot-water draw. This unit's UEF is 0.82, and the fuel is natural gas. The source is DOE CCD, retrieved 2026-09-19. The figure applies only at the high draw pattern; the data give no value for any other pattern. Among 397 models registered as a gas tankless unit at this pattern, the median is 182 therms. This unit is 24 therms above that median and ranks 229th lowest in energy use of 397. That puts it in the second-highest quarter of its class for energy use.

The high draw pattern describes a larger household, or one where showers and laundry overlap. For that kind of use, 206 therms a year is the figure to check against. The registry lists a maximum flow rate in gallons per minute of 4.5. That is a flow limit, and it is separate from the annual energy figure. The unit sits 24 therms above its class median. A reader whose main aim is low gas use may want to compare other models in the class. Models of the same class can be found through same-class replacement by model number. The data do not cover other draw patterns, so this page makes no claim for smaller households.

The running cost is not stated in the text because it depends on the state average residential gas price. That price changes with location, so the page computes the cost from your ZIP. Use the cost calculator on your own ZIP to apply your rate to 206 therms. The method is described in how the annual cost is calculated. Any cost result applies only to the high draw pattern and to 206 therms of natural gas a year. The modeled installed-cost range is shown in its own block with its source and date, and it is not a quote. It is not repeated in this text. A gap of 24 therms from the class median is a difference in therms, and its cost effect depends on the same gas price.