HVAC Expensing and Technology Act of 2017 or the HEAT Act of 2017 This bill amends the Internal Revenue Code to allow expensing and accelerated cost recovery for certain energy efficient heating and air-conditioning property. The bill applies to certain real property: (1) with respect to which depreciation (or amortization in lieu of depreciation) is allowable; (2) which is installed as part of the heating, cooling, ventilation, and hot water systems; and (3) which is within the scope of specified standards of the American Society of Heating, Refrigerating, and Air Conditioning Engineers and the Illuminating Engineering Society of North America.