This story was updated July 18 after the commission’s vote.

South Miami just became Florida’s first city to require new homes to include rooftop solar installations, thanks to a teenage girl who helped write the ordinance. Now, despite facing opposition from a Washington, D.C.-based organization, she’s set on spreading the measure across the state.

The ordinance received initial approval from South Miami’s city commission last week, and was approved on Tuesday by a vote of 4-1. But its origins date back more than a year, to when Delaney Reynolds, then a 16-year-old high school student from Miami-Dade County, read about a similar measure passed in San Francisco, the first major U.S. city to require rooftop solar for new construction.

Reynolds wrote to the mayors of half a dozen cities in her area, urging them to draft similar ordinances. Philip Stoddard of South Miami was the first to respond.

“Climate change is the biggest issue that my generation will ever face in our lifetime,” Reynolds said. “We’re going to be the ones who inherit this mess, and we’re going to be the ones to solve it as well.”

Reynolds had already devoted years to raising awareness about climate change and sea level rise before starting her campaign for solar ordinances. She founded a nonprofit called The Sink or Swim Project, which highlights the climate challenges facing South Florida.

Stoddard invited her to help write the ordinance for South Miami. Since they began, he said, he and colleagues have heard from officials in other cities, including St. Petersburg and Orlando, who are interested in replicating the work.

The ordinance describes several climate threats the Miami area is facing, including its vulnerability to sea level rise and extreme temperatures. Tidal flooding has already forced the city to modify its sewer system, it says. It also notes the city’s 2009 commitment “to implement policies to eliminate net emission of carbon dioxide and other greenhouse gases by the end of 2030.”

A growing number of U.S. cities are taking steps to reduce their greenhouse gas emissions and increase their use of renewable energy. Their ranks have increased since President Donald Trump began rolling back federal climate regulations this year and announced that he would pull the United States out of the Paris climate agreement.

Reynolds’ measure makes South Miami one of only a handful of municipalities nationwide to require solar installations on all new homes, joining San Francisco and at least three other cities in California. It also requires solar installations for any renovations that expand a home by more than 75 percent or replace more than 75 percent of the existing roof.

Robocalls from the Opposition

The ordinance drew some well-financed opposition, however. Last month, Family Businesses for Affordable Energy, a Washington, D.C.-based organization, began running robocalls opposing the measure ahead of the vote. The group also sent a letter to the city commission saying the ordinance would increase the cost of housing and asking it to exempt smaller homes.

The organization’s website says it is a coalition of small businesses supporting lower energy prices. Its executive director, Alex Ayers, has lobbied for the National Association of Electrical Distributors, which represents electric supply companies. Stoddard has accused the group of running an “astroturf” campaign on behalf of the electrical sector, but Ayers said in an email that his group has not received any money from utility companies.

How Much Impact Would the Rule Have?

Stoddard is quick to admit that the measure itself will not have a big direct impact, with only about 10 new homes constructed each year. “This ordinance is not going to save the planet,” he said, pointing out that the city is expanding solar more rapidly by working to create solar co-ops, which help homeowners band together to install their own systems.

But the new ordinance brings attention and the potential to spread. “I think people will beat a path to my door,” he said.