U.S. Department of Energy, Energy Efficiency and Renewable Energy Office (EERE),  Dec. 31, 2013.
http://www.regulations.gov/#!documentDetail;D=EERE-2013-BT-DET-0057-0002

"The U.S. Department of Energy has tentatively determined  that hearth products meet the criteria for covered products because classifying products of such type as covered products is necessary or appropriate to carry out the purposes of EPCA (which is to improve the efficiency of covered consumer products to conserve the energy resources of the Nation), and the average annual U.S. household energy use for hearth products is likely to exceed 100 kilowatt-hours (kWh) per year."