The U.S. Department of Energy (DOE) amended the clothes dryer performance test procedures (10 CFR Parts 429 and 430) to stipulate the Combined Energy Factor (CEF) as the efficiency metric effective September 13, 2013. The CEF includes the active drying cycle energy as well as energy consumed during Stand-by and Off modes.
Due to the changes in the new DOE test procedures, there is no direct conversion of the Energy Factor (EF) to the CEF.
The ANSI/RESNET/ICC Standard 301-2014 Energy Rating Index procedures are based on the clothes dryer Energy Factor (EF) that was the rating in effect before the CEF
According to DOE estimates, under the new test procedures, the Energy Factor of a standard clothes dryer would increase from 3.01 to 4.39. The annual energy consumption for the clothes dryer would decrease from 967 to 684 kWh/yr. To match the annual energy consumption estimates of the new DOE clothes dryer test procedures, multiplying the CEF by 1.15 would meet those estimates. This works equally well for gas clothes dryers. The Energy Factor of the gas clothes dryer would increase from 2.67 to 3.9 while annual energy decreases from 1,091 to 748 kWh/yr.
To provide guidance to HERS software tool developers, the RESNET Standard Development Committee 300 has adopted a formal standard interpretation.  The interpretation provides a means of converting the CEF rating to an EF rating
The interpretation states. “For clothes dryers, the Combined Energy Factor (CEF) multiplied by 1.15 will be used in place of the Energy Factor (EF) for Home Energy Ratings.”
The Clothes Dryer CEF interpretation is posted on the RESNET website at RESNET Interpretation on Clothes Dryer CEF