My crystal ball has no way of projecting beyond 2018 with certainty, but for right now - Yes this would go on 3468. You will find the current best guess for 2019 on the instructions for that form. https://www.irs.gov/pub/irs-dft/i3468--dft.pdf

From the What's New "Phasing out of certain investment credits. The Protecting Americans from Tax Hikes Act of 2015 has implemented the phasing out of the investment credit for solar illumination and solar energy property. The credit for solar illumination and solar energy property is reduced from 30% to 26% for property the construction of which begins after December 31, 2019. See Line 12c, later"