The development is owned by K Road Power, with SunPower now providing operations and maintenance services at the location.
MID will purchase power produced at the site under terms of a 25-year agreement.
The venture created 150 construction jobs and is capable of producing power for around 6,000 homes.
Roger VanHoy, assistant general manager of electric resources at MID, said, 'The McHenry solar project takes advantage of our unlimited solar resource to provide clean, reliable electricity to customers, while helping MID comply with California's renewable energy requirements for utilities.
'When MID buys power generated from utility-scale solar, our whole community shares the promise of emission-free energy from the sun.'
William Kriegel, chairman and CEO of K Road, added, 'The McHenry Solar Plant is a world-class solar project and represents K Road's commitment to own and operate a diversified portfolio of solar PV generating assets under long term supply relationships.
'We are proud to supply clean, renewable electricity to communities served by the Modesto Irrigation District.'