Maine’s utility regulators will likely get an earful Tuesday evening when they hold a public hearing focused on Central Maine Power.

The first of three public hearings the Maine Public Utilities Commission will hold this month will take place in Portland. The hearings are part of the PUC’s investigation of CMP’s billing accuracy and customer service operations and the commission is also weighing a rate increase of about 10 percent that the company is seeking.

The hearing comes about a month after an investigation by the Portland Press Herald found that the company mismanaged the rollout of a new billing system  and created more than 100,000 inaccurate bills.

A lawsuit over the billing practices also has targeted the utility, which delivers electricity to customers in southern and central Maine.

The hearing is intended to give customers a chance to tell the PUC about their experiences as the panel continues an investigation of the company over the billing system. Some customers saw huge spikes in monthly charges, while others didn’t receive bills for months. Regulators are threatening to fine CMP or can order a reduction in its profit margin if they find it broke state rules.

Lauren Loomis, an administrator for the consumers’ group CMP Ratepayers Unite, said said many in the organization think the state should buy CMP and convert it to a public utility – an idea that appeared as a legislative bill last session and was held over for further study.

She said the PUC’s investigation has dragged on too long. It’s been more than 18 months since CMP switched to its new billing system, which critics contend is when the billing problems began.

“Many are still demanding answers for their high bills,” Loomis said, and some members of her group feel the company isn’t providing straight answers. “It’s been 18 months and we’re just now getting a public hearing.”

Loomis won’t speak at the public hearing because she’s a formal intervenor in the PUC’s investigation, meaning she participates in the PUC’s deliberations. She will, however, be at the hearing to gather input from the public on the issues.

PUC officials said they will assess its ground rules for the public hearing Tuesday depending on how many people show up to discuss CMP and enter statements for the commission to consider. The hearing is scheduled to begin at 6 p.m. at Hannaford Hall on Bedford Street.

Harry Lanphear, the PUC’s administrative director, said limits on speaking time will be considered if dozens or hundreds of people show up. The PUC also announced this week that it will accept sworn affidavits in lieu of public statements from those who are unable to attend any of the hearings.

The second hearing is scheduled for Farmington on Thursday and a third is set for Monday, July 22, in Hallowell.