Northern Border Regional Commission Reauthorization Act of 2018 This bill reauthorizes through FY2023 each of the Southeast Crescent Regional Commission, the Southwest Border Regional Commission, and the Northern Border Regional Commission. The bill revises the process for determining the share of the commissions' administrative expenses payable by each state. A commission may make economic and infrastructure development grants to states and local governments, Indian tribes, and public nonprofit organizations for projects to grow the capacity for successful community economic development in its region. A commission must include the development of renewable and alternative energy sources in the categories to which at least 40% of economic and infrastructure development grant amounts are allocated. Such grants may be used to attract businesses to a region from outside of the United States. The Northern Border Regional Commission shall establish a state capacity building grant program to furnish grants to Maine, New Hampshire, New York, and Vermont for specified efforts that include support of business retention and expansion in eligible counties and establishment of programs to encourage job creation and workforce development. The bill adds to such commission: Belknap and Cheshire Counties in New Hampshire; and Addison, Bennington, Chittenden, Orange, Rutland, Washington, Windham, and Windsor Counties in Vermont.