PPA terms tend to be closely held. Mark “JJ” Carnes, business manager at Steelton-Highspire School District, declined to reveal how much the district was paying for the solar power it’s getting, although he did say it’s “pennies compared to what the going rate is.”
That cheap solar power has helped improve the already attractive economics of electricity versus diesel fuel, making the math for EV buses much more attractive. The district expects to save about $20,000 per year thanks to its decision to electrify its bus fleet, Carnes said.
Having the solar next to the high school also helped the district and First Student work through a charging challenge, he said. First Student already had a diesel bus depot in the area, but the site didn’t have the electrical capacity required to outfit it with chargers for the EV buses.
Rather than ask the local utility to undertake the lengthy and potentially costly work of upgrading the depot’s electrical service, “it was natural to say, ‘OK, we have space here — and we have the solar array.’ Why would I pay the grid to charge these buses when there’s a 1.7 megawatt PV array sitting out back?”
Cheap solar power is a good way to improve not just the cost but also the carbon-cutting impact of switching to electric school buses, Kresge said. “If you can take that energy when it’s generated and put it back into batteries, you’re not only not burning diesel fuel in the bus, but you’re also not burning grid power, which also tends to be fossil-fuel driven in many locations.” In 2023, nearly 60 percent of Pennsylvania’s grid power came from fossil gas, and another 5 percent came from coal.
It’s not always the cheapest option, however. Some utilities offer special “time-of-use” rates to encourage customers to charge their EVs when demand for utility power is lower and avoid times when power demand is higher. Those rates may be cheaper than the price that schools are paying for their solar power, he said — and if those times line up with when electric school buses need to be charged, that’s probably a better deal.
It’s also possible that solar power may be worth more going back to the utility grid than it is going into buses, Franklin noted. The value of customer-owned solar power being sent back to the grid varies widely from state to state and utility to utility, and those values can change as policies shift. But it’s worth figuring out which is better when designing a solar-charging plan, he said.
On the other hand, using solar power to charge buses could help schools avoid demand charges, Kresge said. Those are extra costs based on big utility customers’ maximum draw from the power grid at any single point in time over the month or the year. Electric bus chargers can pull hundreds of kilowatts of power, and if they’re all charging at the same time, that can lead to a big demand spike.
“We’re seeing some school districts getting dinged with 150 percent of their previous electrical bill being made up of demand charges,” he said. Solar power flowing onto the same circuits that are powering bus chargers can reduce those demand spikes when the sun is shining.
Not all bus-recharging schedules align with maximum solar output, of course. School districts may also want to see if adding stationary batteries that can store solar or grid power to offset bus-charging loads at other times might be worth the extra cost compared with the risk of demand charges, Kresge said.
Solar, electric school buses, and batteries can also provide backup power, he noted. So-called vehicle-to-grid (V2G) technologies can tap extra electricity from EV batteries to offset grid power consumption. With the right technology in place, they can also be used during blackouts to power lights, air conditioning, and heating for school buildings.
First Student has already started working on this kind of “microgrid” technology at projects like its solar and battery-enabled bus depot in New York City. Similar electric-bus V2G projects are being launched in multiple states, including California, Colorado, Illinois, Maryland, and Massachusetts. Steelton-Highspire School District plans to explore using its electric school buses for backup power, although it hasn’t started that work yet.
All these variables put a lot of pressure on school districts, Tablan said — particularly those that lack an integrated plan for how to deal with them.
“Solar is typically decided by a facilities director, and the decision to electrify buses is made by a transportation director. They’re coordinating these decisions in a different way.”
Generation180’s School Leadership and Clean Energy Network connects districts that have undertaken these kinds of projects with those that haven’t yet, she noted.
Steelton-Highspire School District is still awaiting the first full year of solar and electric bus operations to get the data it needs to fine-tune its approach, Carnes said. “With us being underfunded, we have a number of other five-alarm fires we’re handling,” he said.
“The electric school buses are on the road, they’re running, they’re funded — we have to shift our focus to other issues at the school district,” he said. But he’s planning to take time during the coming summer break to “do a full deep dive on this. I want to know what number of miles per kilowatt-hour we’re getting.”
At the same time, Carnes recommended that school districts don’t wait too long to take action — particularly when delay could mean missing the opportunity to secure government grants.
“This is for all the other underprivileged, underfunded school districts out there,” he said. “You can do it — but you gotta go out and do it.”
