Rheem ECO 8

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.96 for this model. This site computed the annual figure of 615 kWh from that UEF and the DOE test's daily hot-water draw for the very small pattern. It is a computed value, not a measurement. The registry does not publish the annual figure itself. The figure applies only to the federal test's daily draw. A household that draws more or less hot water will use a different amount. The energy data was retrieved from the DOE CCD on 2026-09-19. Measured use in a real home is not available here.

Among the 271 models registered as an electric tankless unit at the very small draw pattern, the median is 615 kWh. This model sits 0 kWh from that median. That places it equal to the median, and the rank above falls in the second-lowest quarter of its class for energy use. The comparison covers only models of the same type and draw pattern. It says nothing about other fuels or other draw patterns. A model with a lower figure in this class uses less electricity at the same test draw. To find a model in the same class by model number, use the same-class replacement search.

The very small draw pattern covers small units - a single bathroom, or a point-of-use heater under a sink. The registry lists a maximum flow rate in gallons per minute of 0.7 for this model. A household drawing more than this pattern is outside what the figure of 615 kWh represents. Running cost depends on your own electricity rate, so the text gives no cost. The cost calculator for your own ZIP applies your rate to 615 kWh. The annual cost methodology explains how that cost is calculated. For other fuels, space or sizes, try the water heater selector.