LOCHINVAR ATO-199B-N 1**

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.82 for this unit. This site, not the registry, computes 206 therms of natural gas from that UEF and the DOE test's daily hot-water draw for the high draw pattern. It is a test-condition figure, not a measurement of any household. The source is DOE CCD, retrieved 2026-09-19. Among the 397 models registered as a gas tankless unit at this draw pattern, the unit ranks 229th lowest energy use of 397. That places it in the second-highest quarter of its class for energy use. The gap from the class median of 182 therms is 24 therms, on the higher side. The calculation is set out on the methodology page.

The high draw pattern describes a larger household, or one where showers and laundry overlap. The 206 therms figure applies to that pattern only. A household that fits it can compare 206 therms with the class median of 182 therms directly. A household with lighter use is not described by this figure, and this page has no value for other draw patterns; that value is not available here. The unit's maximum flow rate in gallons per minute is 5. The registry data shown here does not say how the unit performs when several fixtures run at once. The water heater selector compares units by fuel, space and size.

Running cost is not stated in the text because it depends on the state average residential gas price, which differs by reader. The 206 therms figure is fixed by the test conditions, so the cost is that figure applied to your own rate. The 24 therms gap to the median is also in therms and scales with the same rate. The cost calculator works this out from your ZIP. To compare another gas tankless unit at the high draw pattern, find a same-class replacement by model number. The installed-cost range appears in its own block on this page, as a modeled range and not a quote.