The Department of Energy (DOE) is responsible for defining and implementing energy conservation standards and testing procedures for various equipment and appliances, including water heaters.  Recently the DOE has introduced a new metric for communicating the energy efficiency of residential water heaters called the Uniform Energy Factor (UEF), replacing the previous Energy Factor (EF).  Manufacturers were required to report and share UEF numbers by June of 2017. UEF only applies to residential water heaters. Commercial water heaters will continue to be rated on Thermal Efficiency.

Why are the ratings different?

While both EF and UEF measure the energy efficiency of the water heater, it is the testing procedures that are different. The main difference is that the new test procedure for UEF is intended to better represent how people use hot water today.  

How is the UEF Rating calculated?

UEF ratings are determined by assigning water heaters into one of four categories of hot water based on their usage and then evaluating their performance based on that usage. Each category has a specific hot water draw pattern and a water heater is assigned a category based the hot water delivery capacity.  A greater UEF rating will indicate that the water heater in that category is more efficient. The DOE also has updated the minimum efficiency for all residential tankless water heaters to .81. 

Going forward all Energy Guide Labels will now include updated performance information to help consumers and contractors choose the water heater that best accommodates their needs. It is important that consumers and contractors understand that the change to UEF ratings is only a change to the way water heaters are being tested, measured, and communicated. Rinnai water heaters remain as efficient as they always have been and are built with the same quality that our brand is known for.