The proceedings over Central Maine Power’s latest request for a rate increase have taken another unprecedented turn. On Wednesday, the Maine Public Utilities Commission asked the electric utility to hand over internal documents from its multinational parent company, Iberdrola, which could offer insight into how the company estimates how much it needs to earn to cover expenses and appease investors.

“This appears to be the first time that any multinational corporation in the U.S. has been forced in a rate case to divulge its own internal math,” said Seth Berry, a former Democratic state legislator who now leads Our Power, a nonprofit that advocates for affordable clean energy in Maine and is participating in the case as an intervenor.

The electric utility has asked the Maine Public Utilities Commission for permission to raise distribution rates by an average of $18 per month for residential customers, which would increase the company’s return on equity, currently capped at 9.35 percent, to 9.8 percent.

The Public Utilities Commission already rejected a previous, longer-term request by Central Maine Power in 2025, the first time the commission has outright rejected a utility’s distribution rate proposal.

Rate cases in Maine are run much like court cases, with various parties and intervenors arguing different sides and bringing in expert witnesses. One of those parties is CMP Ratepayers Unite, a group representing customers of the utility who oppose the proposed rate increase. 

The group, after some back and forth with the Public Utilities Commission, was able to use a recent Maine law granting compensation for intervenors to hire expert witnesses. CMP Ratepayers Unite hired Mark Ellis, the former chief of corporate strategy for the California utility Sempra. He has become a vocal critic of utilities’ rate increases and high profits, publishing an influential paper on the topic in 2025 with the think tank American Economic Liberties Project, which advocates against monopolies.

Ellis went through Iberdrola’s annual financial report for 2025 and found a financial analysis that used a discount rate — which approximates the rate of return expected or needed from an investment — of 6.26 percent for its U.S. electric and gas assets, which include Central Maine Power.

Last month, CMP Ratepayers Unite requested Iberdrola’s internal documents laying out the math behind this number, seeking to understand why CMP asked for significantly more — a 9.8 percent return on equity — in its most recent request. Central Maine Power objected to this request, leading to a conference today before the Public Utilities Commission staff. 

This analysis of Iberdrola’s finances “is an entirely unrelated accounting exercise,” said Sarah Tracy, an attorney at Pierce Atwood representing Central Maine Power. It’s about Iberdrola’s existing assets, not future investments, and does not have information specific to Central Maine Power, she said.

But Peter Murray, an attorney at Murray Plumb and Murray representing CMP Ratepayers Unite, argued that the analysis was potentially relevant because experts testifying in the CMP rate case are using a similar process to try to figure out the company’s costs.

“There’s no number that’s been produced so far that’s more relevant in this proceeding than CMP’s parent’s own analysis of the economic risk posed by this investment,” Murray said. 

The other math presented by Central Maine Power so far is based on other, comparable companies.

The requested information is a starting point that should be made available to the commissioners and shouldn’t be closed off to inquiry at this early stage, Murray said.

After hearing the arguments from attorneys representing both sides, Nora Healy, the commission’s presiding officer in the case, decided to overrule Central Maine Power’s objection to sharing these documents. Healy said she hopes the company can share them within a day or two, and that some of the information can be shared confidentially under protective order.

By law, the rate of return a utility company in Maine can earn is supposed to be based on the actual cost of attracting investors, said Rebecca Schultz, senior advocate for climate and clean energy at the Natural Resources Council of Maine, in an email. Schultz is an intervenor in the case. The state PUC sets the rate of return for utilities. 

That cost “is not an easy number for outsiders to guess,” she said. “What CMP will now be forced to make public are Iberdrola’s internal documents, offering a glimpse of what CMP’s owners estimate its cost of capital to be.”

This story was originally published by The Maine Monitor, a nonprofit civic news organization. To get regular coverage from The Monitor, sign up for a free Monitor newsletter here.