Cochin International Airport. (Photo: Binu jayakrishnan/CC0)

Three years ago, managers at the seventh-busiest airport in India began an experiment.

Power bills were costing Cochin International Airport millions of rupees each year, so, with an eye toward lowering that amount, they installed solar panels on terminal and hangar roofs. 

Last year, they decided to get even more serious about solar energy, opting to spend around 620 million rupees, or $9.3 million, on a 45-acre field of solar panels. That plant, which went online in August, now generates over 50,000 kilowatt hours of energy on its best days, which is sometimes more than what the airport needs. 

This means the airport is now completely independent from the electricity grid, and, managers tell CNN Money, saving a lot of money as well. They expect to earn back the 620 million rupees spent on the plant in less than six years, in the form of savings.  

Airports, it turns out, might be perfectly suited to solar power, given that many are surrounded by open space. Managers at Cochin are already planning an expansion.