Heat Efficiency through Applied Technology Act or the HEAT Act This bill directs the Department of Energy to establish model rules and procedures for (1) interconnection and its associated costs; and (2) determining fees or rates for supplementary power, backup or standby power, maintenance power, and interruptible power supplied to facilities that operate combined heat and power technology and waste heat to power technology. ("Interconnection" means service to an electric consumer under which an on-site generating facility on the consumer's premises is connected to the local distribution facilities.) The bill also directs the Environmental Protection Agency to create a voluntary grant program to encourage states to update state or local air permitting procedures to incorporate output-based emission standards. ("Output-based emission standard" means a standard that relates emissions to the electrical, thermal, or mechanical productive output of a device or process rather than the heat input of fuel burned or pollutant concentration in the exhaust.)