The precipitous drop in solar prices has made systems more accessible for U.S. schools than ever before. A full 99 percent of solar installations occurred in the last decade, mirroring the trend line for diminishing costs. 

A new report from three solar advocacy groups -- The Solar Foundation, Generation 180, and the Solar Energy Industries Association -- details the solar surge for schools.

One of those organizations, SEIA, is also using the report as an opportunity to warn about the impact of tariffs.

Since 2008, cumulative PV capacity on K-12 school buildings increased by 86 percent. But because the main driver of adoption is now cost, possible tariffs on imported solar equipment from the Section 201 Trade Case could have a major cooling effect.

“All of the reasons why people are going solar…really tie back to the affordability. Injecting significant additional costs on these projects would poke holes in the very reason that people are adopting solar: that it is affordable and that it is competitive with other fuels,” said Dan Whitten, a spokesperson with the Solar Energy Industries Association. “Artificially raising prices is never a good thing.”

In the three years since SEIA -- along with partners the Solar Foundation and clean energy nonprofit Generation 180 -- began monitoring solar projects at American schools, cumulative capacity grew from 490 to 910 megawatts. The number of schools with installed projects has grown by 46 percent, to a total of 5,500 buildings.

The increase in installations is directly correlated with falling costs for installations. In the past decade, the average cost of a school solar system fell 67 percent.

While school installations remain marginally more expensive than industrial, commercial and community solar systems, schools have been able to take advantage of economies of scale. System size has increased faster at schools than in other non-residential systems.

“That’s one of the huge breakthroughs of this incredible cost drop,” said Whitten. “It really did used to be the case that solar installations on schools were sort of an anomaly or that the school did it more for the civic aspect and less for the cost savings aspect. Now, because of lower costs -- and also innovation in incredible efficiencies in solar, tracking devices, smaller panels -- it really is possible for schools to build much larger arrays.”

Already in 2017, the average school install is twice the size of other non-residential systems. PPAs are a factor too.

Take the arrangement between SunPower and Kern High School District in Bakersfield, California for a 22.7-megawatt project. For the first 20 years, the PPA has a rate of 11.9 cents per kilowatt-hour, which steps down to 7 cents in the last five years of the agreement. The project's large size, low initial investment, and favorable rates compared to utility prices will allow the district of 35,000 students to save $80 million over 25 years.  

“PPA offerings have improved significantly,” said Tom Williard, founder at Sage Renewable Energy Consulting, who worked with the district on the plan. “Lower installed cost and financing innovations have resulted in PPA base prices well below utility energy costs.”

Approximately two-thirds of California districts that invest in solar are financing them through PPAs, said Williard, who was quoted in the report. Nationwide, nearly 90 percent of all school solar systems undertaken in the last three years have used PPAs.

PPAs aren’t an option in every state, though, offering uneven economic benefits around the country.

States with mature solar markets are, unsurprisingly, the ones with the most solar-powered schools. California, the  No. 1 state, has 489 megawatts; New Jersey and Arizona come in second and third with 131 megawatts and 97 megawatts, respectively.

States that have what Whitten calls “regressive policies,” such as Florida and North Carolina, have far fewer schools with installed systems. 

But even in those states, at least some percentage of schools have installed solar. In Florida, American Recovery and Reinvestment Act funding brought 10 kilowatts of solar-plus-storage to schools that can serve as emergency shelters. The Illinois Clean Energy Community Foundation awarded $5 million to schools in the state to build small demonstration systems. In Illinois, 5.8 percent of schools have solar. 

According to Whitten, schools are constructing projects even when polices aren't favorable. After installation, schools can save money on electricity and reapportion those funds to teacher salaries, classroom materials like books, or other expenditures. The installations can serve as a “living laboratory” for kids to learn about electricity and clean energy. And with the increasing prevalence of PPAs and third-party ownership in states where they're accessible, more schools can sign up for solar without having to pony up a large portion of their budget. 

However, new tariffs could pause school installations. Until the Trump administration offers its verdict on the Section 201 trade case, schools and installers can’t fully assess the impacts.

“It’s just impossible to judge until we know what the decision is on 201. […] It could be really bad, it could be good, it could be something in the middle,” said Whitten. “I think you’ll see the same kinds of pauses in market and economic activity in schools that you’ll see in the rest of the economy.”