Lizzie Wade, reporting for Wired:
Like Paraguay, Colombia, Brazil, and many other Latin American countries, Costa Rica gets most of its energy—about 80 percent—from hydroelectric plants. Damming rivers has environmental consequences too, obviously, but the energy from the resulting power plants is carbon-free. Hydropower is also more reliable and easier to scale up than existing wind and solar technologies.
So in that sense, Costa Rica’s 75-day streak may be impressive, but it isn’t surprising, says Juan Roberto Paredes, a renewable energy expert at the Inter-American Development Bank. On average, the country’s energy matrix was already nearly 90 percent renewable, making it the second most “renewable country” in Latin America (after Paraguay, which gets nearly all of its energy from just one dam).
The other 15 percent? Geothermal from the country’s numerous volcanoes.