All ENERGY STAR certified geothermal heat pump models are recognized as Most Efficient, as they deliver superior performance, particularly when it is very cold or very hot. Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Geothermal Heat Pumps that are effective as of January 1, 2012 or the Version 3.2 Program Requirements that are effective as of July 16, 2020. A detailed listing of key efficiency criteria are available at https://www.energystar.gov/products/heating_cooling/heat_pumps_geothermal/key_product_criteria.