The Gorona de Viento plant is due to launch in June on El Hierro, the smallest of the Canary Islands off the Atlantic coast of Africa, project spokeswoman Cristina Morales told news agency AFP.
"It will introduce energy into the system gradually. By the end of this year, if all goes well, we will be able to reach 100 percent" of the power used by the island's 11,000 inhabitants.
The two sets of turbines, one powered by wind and one by water currents, have a capacity of 11.5 megawatts each, far exceeding the total eight megawatts used at peak times on the island.
To test a system of 100 percent renewable energy, the volcanic island of 278 square kilometres (107 square miles) "is the ideal place because it is so small," Morales added.
The plant cost €80 million ($110 million) to build and Morales said the local government hopes to save the same amount over 20 years by using this cheaper renewable energy.
The island is also expected to cut carbon dioxide emissions by 18,700 tonnes and diesel consumption by 6,000 tonnes.
The island authorities own 60 percent of the plant, with 30 percent held by Spanish energy company Endesa — a subsidiary of Italian group Enel — and 10 percent by a local technology institute.
El Hierro also made the news in 2013 when it became the first island in the world to have full free Wi-Fi coverage.