; (II) to the extent practicable, use existing sites where subsurface characterization or geothermal energy integration analysis has been conducted; and (III) each be carried out in accordance with section 988 of the Energy Policy Act of 2005 ( 42 U.S.C. 16352 ). (iii) Eastern demonstration Not less than 1 demonstration project under clause (i) shall be located in an area east of the Mississippi River that is suitable for enhanced geothermal demonstration for power, heat, or a combination of power and heat. (C) Optional program structure (i) In general The Secretary may, pursuant to section 646(g) of the Department of Energy Organization Act ( 42 U.S.C. 7256(g) ), structure the initiative described in subparagraph (A) as a cost share milestone-based payment initiative (similar to the National Aeronautics and Space Administration Commercial Orbital Transportation Services program). (ii) Requirements If the Secretary elects to carry out clause (i), the Secretary shall— (I) request proposals from eligible entities, as determined by the Secretary, that include— (aa) a business plan; (bb) technical details; and (cc) proposed milestones and associated payments; and (II) select projects— (aa) based on the demonstrated ability of the eligible entity to meet the milestones and associated payments described in the proposal of that eligible entity; and (bb) that have the greatest potential commercial applicability. . 6. Authorization of appropriations Section 623 of the Energy Independence and Security Act of 2007 ( 42 U.S.C. 17202 ) is amended by striking $90,000,000 in the first sentence and all that follows through the period at the end of the second sentence and inserting $150,000,000 for each of fiscal years 2020 through 2024. . 7. Reauthorization of high cost region geothermal energy grant program Section 625 of the Energy Independence and Security Act of 2007 ( 42 U.S.C. 17204 ) is amended— (1) in subsection (a)(2), by inserting or heat after electrical power