We have to tread carefully here. This site is intended for use by electricians, electrical contractors, inspectors, engineers, and others who make their living from the electrical industry. We are not allowed to provide support for persons who are not electricians, and who are doing their own electrical installation work. We are required, by the forum's owner, to close any thread that is started by a Do-It-Yourself electrical installer.
But for the moment, at least, I will allow this thread to remain open. You did not ask for assistance in performing or designing an electrical installation. So let's keep the discussion focused on code issues.
My response is that I know of no requirement in the NEC that any building, new or existing, include provisions for the future installation of anything. If there is a requirement that a pipe be installed, in order to facilitate the future installation of a solar panel, that requirement does not come from the NEC. I suggest asking the inspector to give you the chapter and verse of the code requirement he is using to fail your installation. If he can come up with one, it is more likely to be a local electrical code or a building code.