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CONCORD — With 60% of its $75 million solar energy system down, Mount Diablo Unified School District is left with questions about maintenance, repairs and financial losses.
For years, the district has operated what it says is one of the nation’s largest solar energy systems for a kindergarten-12th grade school district. Installed in 2010 using bond money, the system has generated about 11 megawatts of energy annually and saved the district about $17 million in general fund dollars.
A recent inspection by SunUp Solar Tech Service, a solar operation and maintenance company, found that 43 of the district’s 77 inverters are offline. Inverters are key elements of a solar energy system that take direct current electricity and turn it into alternating current electricity, which is the type of energy used by the power grid, according to the U.S. Department of Energy.
Without the 43 inverters, the district is losing out on about 7,860 kilowatts of electricity, or nearly eight of the 11 megawatts promised in the past.
SunUp Solar identified the mechanical issues that have stunted the system, said Melanie Koslow, the district’s executive director of Maintenance, Operations and Facilities, who presented the firm’s findings to the district’s Board of Education on Wednesday.
Details of the financial impact from the outages are still unclear, though Koslow estimates that the district has spent about $2 million more annually on energy. Capital Engineering, a mechanical, electrical and plumbing engineering firm the district has worked with in the past, has been tapped to help assess the district’s losses and develop a plan for remedying the issue.
Koslow said she expects to be back before the board in September with more details.
“What we have learned from this assessment is the cost of our systems being down is significant. The cost to bring them up is also going to be significant,” Koslow said.
It’s still unclear exactly how the solar panels are now in such poor condition.
SunPower Corporation, a major national solar company at one time, was awarded a $65 million contract in 2010 to install, monitor and maintain solar panels at 51 district sites. An additional $9.9 million was added to the project price tag a year later to account for some plan reconfigurations to account for a future heating, cooling and ventilation system project, among other needs. The project was paid for with funds from Measure C, a $348 million bond measure approved by voters in 2010.
The contract came with a 20-year performance guarantee and the promise the district would save about $192.5 million over 30 years. The project was completed in 2012.
Twelve years after making those promises, SunPower Corporation filed for Chapter 11 bankruptcy in August 2024. By September 2024, it had sold off key assets to Complete Solaria for $45 million. Complete Solaria rebranded to SunPower Inc. in April 2025.
The district did not immediately respond to questions about who was responsible for system maintenance following SunPower’s bankruptcy. Asked by Trustee Linda Mayo about whether the system may still be under warranty, Koslow said conversations with previous vendors fell apart, but she has leads on a possible answer to that question.
“No one has quite figured it out yet,” Koslow said. “Hopefully, what we’re discovering here will maybe help some of our other districts.”
The district was warned about issues with the solar panels as early as the fall of 2024, when Schneider Electric, another firm behind a separate project that promised energy savings, told officials during a Board of Education meeting that about 30% of the panels appeared to be down.
Members of the Citizen Bond Oversight Committee responsible for monitoring Measure C funds have also repeatedly raised concerns about the district’s power usage.
The contract with SunUp Solar for the solar panel inspection wasn’t approved until March 25.
“The district dropped the ball anyway you look at it,” said Jim Walsh, a former member of the Measure C Bond Oversight Committee. “The incompetent leadership is mind-boggling.”
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