WATERFURNACE. Available in seven single-speed sizes and five dual-capacity sizes, Envision geothermal heat pumps received the Energy Star Most Efficient 2012 designation. All units in the line utilize the ozone-safe R-410A refrigerant and feature-coated air coils for durability and longer life. A microprocessor control sequences all components for optimum performance and provides easy-to-use troubleshooting features with fault lights and on-board diagnostics, the firm says. 800.436.7283. www.waterfurnace.com.