LOCHINVAR ENS-40 1**

The figure of 3,531 kWh a year comes from this site's own calculation, not from the registry. It combines the registry's UEF, the ratio of hot water delivered to energy used, with the DOE test's daily hot-water draw for the medium pattern. For this model the UEF is 0.92. The medium pattern stands for a typical mid-sized household, including a busy morning. The UEF source is the DOE CCD, retrieved 2026-09-19. The annual value holds only at that test draw. It does not describe a home that draws a different amount of hot water each day. The method behind the annual energy and cost figures shows each step, from the registry's UEF to the yearly value.

The registry lists this unit with a rated volume of 37 gallons. Its first hour rating, the gallons of hot water available in the first hour from a full tank, is 55 gallons. The energy figure therefore describes a household whose busiest hour stays within about 55 gallons of hot water. A household that often needs more than that in one hour is outside the condition the figure describes. For that case, the water heater selector by fuel, space and size filters models by those needs. If you are checking a like-for-like swap for this model, you can find a same-class replacement by model number. It lists other electric tanks at the medium draw pattern.

Among the 426 models registered as an electric tank at the medium draw pattern, this unit ranks 213th lowest for energy use. Its 3,531 kWh a year equals the class median of 3,531 kWh, a difference of 0 kWh, under the same test draw. The running cost is not given in this text, because it depends on your own utility's electricity tariff. It is not estimated here. The running-cost calculator for your own ZIP applies your local rate to 3,531 kWh. The installed price range appears in its own block on this page, with its source and date. It is a modeled installed-cost range, not a quote, and its figures are not restated here.