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Montana’s largest rooftop solar array goes live at Missoula County jail

Over 1,100 panels lay on the ideal high and flat surface of Missoula’s prison. The system is expected to produce over 400 kilowatts. (Photo courtesy of Onsite Energy)

On an appropriately sunny afternoon, folks gathered outside the Missoula County Detention Center on Wednesday to celebrate the largest solar installation in the state, which went live on Friday.

The rooftop solar installation includes 1,152 individual panels and was purchased with a unique public-private financing system that shifted much of the initial costs to a private energy company.

“It’s important to note that this biggest solar array in the state was done without a complementary large outlay of taxpayer money,” said Missoula County Commissioner Josh Slotnick.

Saroc Energy purchased the solar array, leaving Missoula County with no up-front costs. The company is eligible for federal solar tax credits based on the purchase. The county will reimburse Saroc for energy the solar array produces over the first five years and will eventually buy the panels at a depreciated cost, said Diana Maneta, the county’s sustainability program manager.

Commissioner Josh Slotnick, left, said the project went “round and round” through the partners involved before sticking and eventually succeeding. (Keely Larson/Missoula Current)

The installation is expected to last 25 years and save the county $400,000. The 25-year timeframe aligns with the lifecycle of the roof itself. Once the roof needs to be replaced, the county can decide whether to reinstall the panels or consider new technology, Orion Thornton, founder of OnSite Energy, said.

The installation took OnSite three months and covers two layers of the long, flat space atop the prison. It is expected to generate over 400 kilowatts of electricity.

The prison uses the most energy of any county building. In 2019, Missoula County declared a goal of carbon neutrality for county operations by 2035. A 100% clean electricity goal was also adopted by the city and county of Missoula with 2030 as the deadline.

Currently, 65% of electricity within the Missoula urban area is clean, according to Maneta.

“What started out years ago as a few of us on the rooftop, realizing how much sunlight is up there, how bright it is — especially if you forget your sunglasses — we saw the potential of the space,” Missoula County Sheriff TJ McDermott said.

The panels will produce 20% of the electricity used within the prison. Due to its size, all the energy produced will remain within the facility and will not be added to the electrical grid. The panels will never produce more energy than the prison needs, Slotnick said.

Partnerships and the inspiration of citizens, local government and private companies enabled the county to reduce energy in two ways, Slotnick said — one related to sunlight and one to inertia.

“We can change how we do business,” said Slotnick. “But only with some vision and some commitment and most of all a whole lot of cooperation. And that’s what we saw here today.”