Maine’s coveted 207 area code has gotten yet another extension, this one “perhaps indefinitely,” the state’s top regulator said.

The Public Utilities Commission voted 3-0 on Tuesday to authorize Consolidated Communications of Northern New England Co., the largest carrier in the state, to consolidate its 135 rate centers into one. The groupings of telephone exchanges represent nearly half of the state’s 249 rate centers, and consolidation will reduce demand for new telephone numbers that has followed the explosive growth of cellphones and Voice over Internet Protocol, which allows people to make calls online.

Chairman Philip Bartlett said the consolidation would ease pressure on the state’s sole area code, which officials have previously warned could only have a few more years left. The move should free up thousands of 207 phone numbers.

“Accordingly, I’d approve rate center consolidation and may long live the 207 area code,” he said. “With this, we think we can potentially extend the 207 area code well into the future, perhaps indefinitely.”

Rate centers, which help phone companies calculate call distances and costs, are generally associated with the three digits that follow the area code. The rate centers often, but not always, correspond to local or municipal boundaries. Initially, they were used to group numbers geographically for billing purposes.

While 10,000 number combinations are possible among the last four digits of a phone number, carriers are assigned groups of 1,000 numbers once they use at least 100 within a given run of three middle digits. That can tie up phone numbers and prevent carriers from assigning them, even if they are not in use.

The commission began investigating the feasibility of a large-scale rate center consolidation in January 2023. The number of service providers in Maine today “far exceeds what the architects of Maine’s original numbering plan for 207 would ever have envisioned,” Bartlett said.

Commissioner Patrick Scully said the scale of consolidation will be the “greatest in the country that we’ve seen so far, and hopefully will be a model for other states that would as well like to avoid unnecessarily adding additional area codes.”

The consolidation is expected to be completed by the end of 2025, Bartlett said. Conceding that the project will encounter “some uncertainties” and have an impact on other carriers, the PUC directed its staff to update the commissioners and others regarding the progress of the consolidation, the timeline and unanticipated costs, savings and technical challenges.

The costs to consolidate the rate centers are not available. Sarah Davis, vice president of market development at Consolidated Communications, said the company has been waiting for PUC approval before outlining the costs. The company’s first tasks, she said, will be “sizing the effort, figuring out what we do.”

The state Office of the Public Advocate urged regulators to put off a decision until Consolidated Communications provides cost estimates and the PUC has determined that the costs are reasonable.

“The OPA endorses and appreciates the importance, meaning and significance to Mainers of the single 207 area code,” the public advocate said in a Nov. 1 filing with regulators. “However, Mainers also deserve a transparent explanation of how much it will cost and how it will be paid for.”

The cost could be high, and reviewing and challenging the costs after they have been incurred will be “significantly undermined” by not requiring Consolidated Communications to first provide estimates, the public advocate said.