In this March 9, 2019, file photo, a solar farm is seen in Tremont. Credit: Bill Trotter / BDN

Facing an uproar from the solar power industry, Central Maine Power told regulators that it has found faster and less costly ways for large solar projects to connect to the power grid.

CMP announced the change in a letter sent to the Public Utilities Commission on Tuesday, a day after Democratic Gov. Janet Mills called for an investigation. In the letter, CMP said it’s notifying solar farm developers of its “revised approach.”

The state’s largest electric utility originally warned the developers of 18 solar projects that it had underestimated the cost of infrastructure upgrades needed to connect to the grid. The utility had said the upgrades were needed because it had encountered unexpected voltage problems at its substations.

In its letter, CMP said it originally took a traditional engineering approach to interconnections at substations and estimated it would cost millions of dollars for the 18 solar projects. CMP said Tuesday it now believes that “lower-cost upgrades or the complete elimination of upgrades” may be possible with further study.

“These alternative solutions for protecting the system at distribution substations can be engineered and deployed more quickly and cost-effectively,” David Flanagan, CMP’s executive chair, and Douglas Herling, president and CEO, wrote in the letter. The revised total is expected to be “below $40 million” to fix the problems, they said.

Jeremy Payne, executive director of the Maine Renewable Energy Association, told the Portland Press Herald that he’s encouraged by the new development but said an investigation is still warranted.

He also warned that any additional costs are unacceptable for solar developers who’ve lined up financing and in some cases have completed projects that are ready to operate.

“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,” Payne said.