An unprecedented number of schools are using solar energy.

Approximately 3,750 U.S. schools out of a total of nearly 130,000 used solar energy in 2014, according to a survey by two solar energy organizations. However, that number is increasing.

The number of U.S. schools using solar power has more than doubled in the last seven years, reaching roughly and charter K-12 schools and serving more than 6 million students nationwide, according to the fourth edition of the “Brighter Future” report, which was released last week by the clean energy nonprofit Generation180.

The report’s principal author, Tish Tablan, director of Generation180’s Solar for All Schools initiative, called the figure “an astounding milestone.” Some schools are investing in new rooftop and ground-based solar arrays, while others are joining community solar programs. Schools equipped with solar panels in some cases produce enough electricity to sell it back to their local communities. Since 2015, the total solar energy capacity of American schools has nearly tripled to 1,644 megawatts, which is sufficient to supply all the homes in a city the size of Boston, Denver, or Washington, D.C. with electricity.

California is in the lead; the Golden State has the highest solar capacity as well as the most solar schools overall.

It ranks fourth in terms of the proportion of schools using solar energy, behind only Connecticut, Washington, D.C., and Hawaii, where 40 percent of schools use solar energy. And other states are achieving significant success. Between 2019 while 2021, Washington state’s solar capacity increased by more than eight times, and it increased by at least twice as much in Wisconsin, Illinois, Arkansas, and Virginia.

According to Tablan, third-party financing arrangements like power purchase agreements, or PPAs, have made this rise possible in large part. In these arrangements, solar panel installation and maintenance are paid for by developers, while schools purchase the electricity produced for a defined period of time. The agreements give developers a constant stream of income and enable them to benefit from federal tax credits, which is advantageous to them.

The agreements can save schools tens of thousands of dollars each year on electricity costs and eliminate the upfront expenditures of installing solar panels, which the Generation180 report calls “essential” to the spread of solar energy beyond the wealthiest school districts.

According to the report, as of 2021, 47% of public schools that use solar energy are qualified for federal Title I Schoolwide Program funds, meaning that at least 40% of its pupils come from low-income families. 57 percent of all public schools in the country are eligible for this financing as of 2019.

For instance, Colorado’s Denver Public Schools, which serves 90,000 students, installed 9 megawatts of solar power capacity at 50 schools, at least 21 of which are home to Title I Schoolwide Programs, thanks to PPAs with various solar companies. As a result, the district has reduced emissions each year by an amount equal to removing 2,175 gasoline-powered cars from the road.

Additionally, Denver schools are utilizing solar panels to instruct pupils about renewable energy. As a sort of early job training for aspiring electrical engineers, Denver Public Schools collaborated with a nonprofit solar installation this summer to give practical engineering coursework and career assistance to high school students. The program “opened my eyes and introduced me to occupations I didn’t know existed,” according to Kimberly, a student who participated in the Generation180 report’s interview process.

Even though schools have made progress, Generation180 notes that more has to be done because solar panels are still not present in almost 90% of American schools. The organization estimates that switching all of the United States’ K-12 schools to 100 percent solar power would eliminate 60 million metric tons of carbon dioxide emissions annually — roughly equivalent to the yearly climate pollution of 16 coal-fired power plants. “We still have a long way to go to reach the goal of 100% clean energy,” the report states. “And the speed and scale of the climate crisis calls for us to respond faster than ever.”

More PPAs, according to Tablan, might help move the needle ahead and have a particularly big impact on policies in the six states that ban these third-party financing options, largely in the South. This year’s Inflation Reduction Act and last year’s Bipartisan Infrastructure Law, which together provide hundreds of millions of dollars in grants to improve schools’ energy systems and lessen their climate pollution, as well as an expanded tax credit to assist schools in defraying the cost of new solar and battery storage projects, may also be of assistance.