Famed San Francisco columnist Herb Caen once said, “A city is not gauged by its length and width, but by the broadness of its vision and height of its dreams.” When it comes to solar power aspirations, so many of America’s biggest cities should be judged positively, according to Environment America Research & Policy Center’s just-released Shining Cities 2019: The Top U.S. Cities for Solar Energy.

The sixth annual edition of this comprehensive survey of installed solar photovoltaic (PV) capacity in major U.S. cities found that solar energy capacity more than doubled in 45 of America’s 57 largest cities over the past six years. And, some cities saw even more growth. One-third of large municipalities surveyed throughout that period more than quadrupled their installed solar PV capacity.

The findings are encouraging and add to the evidence that cities are leaders in the nationwide shift toward clean renewable energy sources like solar. These results shouldn’t be surprising. Cities possess millions of available rooftops and have all of the necessary infrastructure already in place. Plus, solar initiatives have earned enormous public support.

But much more is possible. This report is a reminder that most cities have only begun to tap their solar energy potential. With smart local policies to encourage solar development on city buildings, homes and businesses, America’s metro areas have a golden opportunity to make solar energy the new normal.

We have enough solar PV capacity to power nearly 1 in 11 American homes today and the technical capability to cover the annual electricity needs of more than 121 million American homes, which is nearly the entire country. To do this, we need to take full advantage of every small building rooftop.

Given cities’ vast potential, local governments should use every tool available to support and encourage solar energy development. At Environment America, we’re rolling up our sleeves to help through our Go Solar campaign. Here’s a snapshot of what we’re up to:

Our Mayors for Solar Energy project is building a broad, bipartisan community of municipal leaders committed to this issue. To date, 235 U.S. mayors and local officials — representing cities from all 50 states — have joined the project. From Dubuque, Iowa, Mayor Roy Buol to Minneapolis Mayor Jacob Frey, they have resolved to make solar energy a key element of their communities’ energy plans, given the many benefits it offers.

We’re also providing the resources and peer-to-peer learning opportunities that will enable communities to take concrete steps toward a brighter, healthier future:

Each edition of our Shining Cities report offers rankings and historical analysis that gives cities context on how they’re doing nationally and helps spark a race to the top among the nation’s biggest metro areas.

Our new solar policy toolkit, Ten Ways Your Community Can Go Solar,details how cities can lead by example, expand access, remove obstacles and work with other institutions to harness more solar energy. These policy solutions are essential, as research shows that good policies are even more important than the availability of sunshine for solar success.

We launched a Mayors for Solar Energy webinar series, which delivers a deeper dive into local solar policy tools and features leading solar community experts who can share strategies and lessons learned with others aiming to emulate successful programs.

These efforts are working. In addition to the growth in solar capacity that each Shining Cities edition uncovers, we’re earning bold commitments to renewable energy from cities across the country:

All of this progress in cities, as policy laboratories, has made it easier for states to follow suit. For instance, before New Mexico’s and California’s landmark statewide commitments to 100 percent zero-carbon energy, cities laid the groundwork and created opportunities for state legislators to act boldly.

As our Shining Cities 2019 report shows, cities have already played a critical role as clean energy leaders, but need to do more. With the tools we’re offering, I can’t wait to see what local governments accomplish in the coming year, and look forward to a Shining Cities 2020 report full of more good news.