While only 20% of airports across the country have adopted solar energy in the last decade, Denver International Airport has become one of the largest solar projects in the country, a University of Colorado Boulder study shows.

The study, which looked at 488 public airports in the U.S., found nearly 100 used solar panels. At DIA, more than 42,600 solar panels have been installed across 56 acres since 2008, the study reported.

The airport’s success in adopting solar energy can be credited to support from city government, airport leadership and its electricity provider, airport officials told researchers.

The airport pays less than the average electricity cost for the energy generated from the solar arrays built after 2012, the study found. Excess energy is sold back to the electricity provider through a rewards program.

“DIA’s solar energy project is an example of successful collaborative partnerships,” said Serena Kim, a researcher at CU.

Through her study, Kim found that airport solar energy is more likely to be used among investor-owned utilities, which have greater resources and expertise to invest in renewable energy.

“Accessing clean, reliable, and affordable energy is integral to resilient, sustainable, and equitable futures,” Kim said. “Policymakers who wish to facilitate on-site solar use should consider strategies for addressing resource and information gaps across investor-owned utilities, municipal utilities, and rural electric cooperatives.”