Greek islands depend on tourism and 13 expressed interest in being the first "green island" in Greece when the plan was initially announced two years ago, Makris said.
Ai Stratis, one of the islands used as exile points during the military dictatorship of the 1970s, was picked because of its small size of 42 square kilometers (16 square miles).
Public Power Corp SA, Greece's biggest electricity producer, has two units on the island. They will remain in operation in case the renewable sources fail.