GeoSpring Hybrid Electric Water Heater - Thermal Efficiency (TE)

"Thermal Efficiency" is used for Commercial water heaters, in addition to "Standby Loss."

Residential water heaters use "Energy Factor" (EF) to measure efficiency, which incorporates a simulated usage test that includes Thermal Efficiency, Standby Loss and Cycling Loss. The EF metric can easily be used to estimate annual operating cost and is used to determine what is listed on the product's Energy Guide:http://www.energy.gov/energysaver/estimating-costs-and-efficiency-storage-demand-and-heat-pump-water-heaters

For an easy method to compare products, see the government's Energy Star website:

Energy Star Certified water Heaters

Note: There are no standard electric water heaters that meet the Energy Star criteria.