Solar panel maker TenKsolar will build a solar power system with 16,000 panels for a Massachusetts municipal utility -- the largest project ever for the Bloomington company.

TenKsolar CEO Joel Cannon said Thursday that the project will cost about $10 million to build on 12 acres in Ashburnham, population 6,300, about 60 miles west of Boston.

The unit will generate 3 megawatts of electricity, enough to power about 300 homes, and is expected to be in service next year, the company said. Its output would be three times greater than Minnesota's largest solar array, the 1-megawatt system atop the Bloomington Ikea store. A 2-megawatt system is under construction by Ecos Energy in Slayton, Minn. (Neither project uses TenKsolar panels.)

The power will be sold to the Ashburnham Municipal Light Plant, the town's utility, under a long-term power-purchase agreement.

Cannon said TenK Energy, a newly created unit, is developing the project and is negotiating with a merchant power company to take ownership and management on completion.

Building the 16,000 panels will require ramping up production at TenKsolar's 72-employee plant in Bloomington, Cannon said. Its panels are manufactured partly at a factory in China, then shipped to Minnesota, where electronics, frames, racks and reflective system are added.

"This will be the biggest one we have built," Cannon said.

TenKsolar, founded three years ago, had focused on selling its solar arrays to others. Cannon said this is the first energy development venture by TenK Energy, created last summer.

TenKsolar's rack-mounted system features a 3M reflective coating on each panel's back side. The coating reflects extra light on the panel behind it, which TenKsolar says boosts power output by 30 percent.

Ashburnham utility manager Stan Herriott said the town's 100-year old power company wants to diversify its energy supply and reduce reliance on market purchases, whose prices it can't control.

"It gives us control over that portion of our power supply for the next 20 years, which we won't have in the open market," Herriott said of the solar array. "Hopefully, when we hit that hot day in July, our solar array will be producing as close to peak as possible."

David Shaffer • 612-673-7090