Things at Whole Foods are about to get even greener.

The grocery chain plans to install as many as 100 rooftop solar systems, mainly through the power provider NRG Energy, on nearly a quarter of its stores and distribution centers, the companies said on Tuesday. SolarCity will also provide systems for the grocer, which could expand the rooftop solar program as the installations proceed.

“Installing solar at Whole Foods locations across the country will increase the percentage of renewable energy that is generated in communities where we work,” Kathy Luftus, global leader in sustainability at the company, said in a prepared statement. NRG plans to install systems in nine states, including California, Colorado, Connecticut, Massachusetts, Nevada and Texas.

Solar energy is in keeping with the Whole Foods image but it will also save the company money, because the solar providers can offer electricity at prices below what the stores and centers would normally pay utilities.

The grocer has been under pressure to reduce costs as it has faced increasing competition from other chains offering specialty and organic foods at lower prices.