You’d think given California’s high renewable energy standard of 33 percent by 2020, and its reputation as the greenest state, would host the city with the greenest energy supply, perhaps in a city like San Francisco, but it doesn’t. Late last month, among large municipalities, Houston took over that title when it chose to purchase 50 percent of its energy from renewable energy sources starting—July 1 till June 30, 2015.

Last month Houston signed an agreement with NRG Energy’s Reliant Energy to purchase more than 140 megawatts of renewable energy. “Houston is already known as the energy capital of the world, but we are committed to becoming the alternative energy capital of the world as well,” said Mayor Annise Parker. “Purchasing green power reduces the environmental impacts of electricity use, decreases the cost of renewable power over time and supports the development of new renewable generation. A triple win for Houstonians,” she said.

Under the new agreement Houston is purchasing renewable energy credits (RECs) from Reliant that are largely generated by wind turbines. The RECs will add little to the city’s energy spend, less than 1 cent per kilowatt hour more than what it would otherwise pay for electricity, the city said. In all, it will add about $2 million to the city’s energy bill.

While Houston is now the largest municipality to make a major purchase of renewable energy, it doesn’t have the highest percentage of its electricity coming from renewables. That distinction goes to Oak Park, Ill., which source 91.9 percent of its electricity from renewable energy. Nor does it purchase the most green energy in the U.S., that distinction is currently held by Washington, D.C., which buys more than 1 million megawatt hours of green energy annually, according to the Environmental Protection Agency’s Green Power Community Challenge Rankings, which were last updated June 14.

Houston’s purchase of green energy, however, is in addition to it’s other green energy efforts. “With existing installations at the George R. Brown Convention Center, City Hall Annex, Discovery Green, and most recently, the Houston Permitting Center, the city is a test bed for solar technologies,” it said.

Houston also taking other efforts to become more sustainable, both as a municipality and for its residents. It is using a SunShot Initiative grant in partnership with the Houston Advanced Research Center in an attempt to streamline and refine the solar permitting process in the city. It is trying to make it even easier for residents to go solar through a Solar Benefit program it’s now investigating. “This idea would reduce the complexity and cost of residential solar through a collective group discount program. The program would reach the residential sector via targeted outreach through employer organizations in Houston,” the city said. The city also has 17 mobile solar-powered units to help the city respond to disasters. While not otherwise in use, the generators are located at fire stations, parks, neighborhood centers and schools.