ORBEK HW100

The figure of 95 therms is computed by this site, not published by the registry. It combines the registry's UEF, the ratio of hot water delivered to energy used, of 0.81 with the DOE test's daily hot-water draw for the low draw pattern. The source is DOE CCD, retrieved 2026-09-19. Ranked by energy use, the unit is 7th lowest of 10 models in its class, which places it in the second-highest quarter. It sits 2 therms above the class median of 93 therms. The figure applies only at the federal test's daily draw, and the method behind the annual cost is documented separately. Measured use in a real home is not available in this data.

The 95 therms figure fits a reader whose household matches the low draw pattern, because it was computed for that draw and no other. The unit's maximum flow rate in gallons per minute is 2.5. This data does not say how many fixtures that flow can serve at once, so that is unknown here. A larger household falls outside the low draw pattern, and this page does not show the registry's figures for higher patterns. Against the class median of 93 therms, the unit is 2 therms higher, and this data does not show what that gap costs. A reader still choosing between fuels or sizes can use the water heater selector by fuel, space and size.

The running cost is not written in the text because it depends on your state's average residential gas price. The page computes it from your ZIP, applying that price to 95 therms of natural gas at the low draw pattern. You can repeat the calculation with the cost calculator on your own ZIP. Any other rate or draw pattern gives a different result than the figure shown. The installed-cost range appears in its own block with its source and date. It is a modeled range, not a quote. To compare HW100 with others of the same class, you can find a same-class replacement by model number, which lists models registered under the same 10-model comparison basis only if they share the fuel and draw pattern.