Reacting to an uproar from solar developers and criticism from Gov. Janet Mills, Central Maine Power said Wednesday that it has found faster and less costly solutions that will allow more large solar projects to hook up to its electric distribution network.

CMP’s fast pivot is outlined in a letter sent Tuesday to the Maine Public Utilities Commission, a day after Mills asked the agency to open an investigation into why CMP belatedly told solar farm developers that their projects are causing voltage-related problems at substations that in some instances could require multimillion-dollar upgrades.

In her letter to the PUC, Mills said she was especially concerned that some solar projects were already built and ready to operate, “and it is deeply regrettable that CMP apparently did not anticipate these issues at the time they entered into these interconnection agreements.”

Mills’ request followed news of the interconnection controversy first reported last week in the Portland Press Herald.

Responding to Mills’ letter, CMP’s top executives said that as they saw costs climb over the past several weeks, they instructed the company’s interconnections team to look for solutions outside of the conventional, more conservative engineering approaches for assuring the safety and reliability of the distribution system. They acknowledged that the mounting and unexpected costs of using a “traditional utility approach to protect the grid” has caused confusion and concern in the solar industry, notably among 18 projects that received revised cost estimates totaling millions of dollars.

“These alternative solutions for protecting the system at distribution substations can be engineered and deployed more quickly and cost-effectively,” wrote David Flanagan, CMP’s executive chairman, and Douglas Herling, the company’s president and chief executive. “Further, CMP believes lower-cost upgrades, or the complete elimination of upgrades, may be possible with further study. Specifically, where initial estimates were $10-$15 million per substation reflecting a complete rebuild of the substation, estimates for all but a limited number of substations are now in the range of $175,000 to $375,000 for those substations that will require upgrades.”


Flanagan and Herling said the new estimates are based on upgrades to add voltage protection and circuit breakers on the transmission and distribution systems.

“The revised aggregate cost estimate is below $40 million to address the entire issue,” the CMP executives wrote.

Representatives of Central Maine Power say that the substation off Two Rod Road in Scarborough is not currently equipped to handle the wave of proposed solar projects. Derek Davis/Staff Photographer


After viewing CMP’s response letter Wednesday, the head of a trade group representing many solar developers said he was encouraged, but he stressed that an immediate PUC probe is still needed.

“We are still deeply troubled by what led to this problem to begin with,” said Jeremy Payne, executive director of the Maine Renewable Energy Association. “What happened with their internal interconnection process? Why wasn’t this found sooner? Why weren’t implicated projects notified immediately?”

Payne also said any new costs, on top of those already agreed to in signed interconnection agreements, put an unacceptable burden on developers.


“How do they expect projects with signed interconnection agreements – and in some cases fully built projects – to absorb these new costs?” Payne asked. “Even if the costs are suddenly less than tens of millions, many projects are fully financed and there is no ability for them to take on these new costs.”

The co-founder of one company affected by the revised costs, Dirigo Solar of Portland, said he was glad that CMP was taking responsibility for solving the substation voltage issue. But that’s only half of the problem.

Aside from assessing the impact of individual solar projects on substations, CMP is performing so-called cluster studies in areas where many projects at once are vying for connections.

“This doesn’t change the fact that CMP promised the completion of many of these studies in 2020,” said Bob Cleaves, a co-founder and principle investor in Dirigo. “And as recently as yesterday, they were telling solar developers that they are unable to say when studies will be completed or what the upgrades will cost, or when the upgrades will be done, and also suggesting that it could take until 2024 or later.”

Mills’ energy director, Dan Burgess, said the proposed cost reduction is a good step, but he echoed the call for the PUC to look into the details.

“As the governor outlined in her letter,” Burgess said, “the administration is interested in understanding the root causes of this issue and finding timely solutions. These issues are vital as we seek to meet the state’s clean energy and climate goals in a cost-effective manner, as is ensuring our electric utilities have the systems and planning in place to accommodate the future growth of solar and other distributed energy resources.”


Catharine Hartnett of Central Maine Power talks about the company’s substation off Two Rod Road in Scarborough on Wednesday. Derek Davis/Staff Photographer


The controversy is evolving quickly, as scores of solar developers are building and proposing projects in Maine worth hundreds of millions of dollars. CMP alone has more than 600 projects seeking to hook up to its system. Not all will get built for various reasons. But the demand has caused a logjam that the company is struggling to manage.

The unprecedented activity is being spurred by recent state policies and laws aimed at encouraging a rapid shift from oil and gas to renewable electric power for running cars and heating buildings. The state’s new Climate Action Plan, a blueprint for how to electrify Maine’s economy, reduce carbon emissions and prepare for a changing climate, strongly encourages solar development.

But hooking up all that solar, plus wind and other renewable power generation, presents a challenge for an electricity network that was designed a century ago to move power one way – from large power plants to customers. It wasn’t built to move energy back and forth from small, intermittent power producers, a process called distributed generation.

To distribute that power from large, high-voltage transmission lines to customers, electric networks rely on substations, such as one CMP built 20 years ago next to the Maine Turnpike in Scarborough.

The Press Herald visited the substation on Wednesday with CMP technicians. It’s one of more than 100 substations in CMP’s service area that has the potential to trigger a voltage problem if  interconnected to a small up-and-down generator.


The Scarborough unit is a distribution substation that taps into transmission lines. It lacks some of the switch gear and protection of larger substations on the transmission side of the network. It was built mostly to send power to homes in the fast-growing town.

The substation features a transformer that steps down voltage from the transmission lines. The lower-voltage power moves through special circuit breakers into regulators that precisely and automatically control the voltage level, depending on overall customer demand that varies every minute. Failure to regulate the voltage could lead to damaged computers, televisions and other electronic equipment. It also could hurt the substation.

CMP’s interconnection queue shows that a developer is planning to build a 4.9-megawatt solar project that would feed into the substation. The document indicates that an impact study was done a year ago and an interconnection agreement was signed in April.

Attempts to identify and contact the developer were unsuccessful Wednesday.

Initial studies indicated a high cost to rebuild and protect the substation. But Chris Fullarton, who manages large interconnection projects for CMP, said engineers have come up with a less-expensive solution.

“We want to integrate renewables,” Fullarton said, “but we can’t have more risk to reliability and safety.”

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