PORTLAND, Maine (AP) — The agency that represents the interests of Maine utility customers is skeptical of a electric utility's proposal to spend hundreds of millions of dollars to "harden" the power grid in the face of increasingly intense storms.

Avangrid, the parent company of Central Maine Power, will have to justify such a large expenditure over 10 years and ensure that ratepayers won't bear the lion's share of the costs, public advocate Barry Hobbins said.

"They have a long way to go to prove to me that they need that kind of money," he said.

Avangrid is proposing a $2.5 billion effort in Maine and New York, and at least some of the costs would be borne by ratepayers under the proposal.

Gail Rice, spokeswoman for the utility, said cost details are still being sorted out. But she said the company wanted customers to know a plan is in the works to boost the reliability of the Maine power grid.

The power company is currently involved in a case to recoup some storm cleanup costs from last fall. Nearly 500,000 utility customers were in the dark at one point, making the number of power outages worse than the infamous Ice Storm of 1998.

The utility believes that such storms are becoming more common and more powerful.

"We've had a lot of very severe storms. They've turned into the new normal," Rice said.

The new plan includes the installation of new poles, insulating wires that might touch trees and more tree-trimming, Rice said. During the October storm, about 80 percent of the damage was caused by fallen trees.

CMP isn't just dealing with infrastructure improvements. The company is also in the midst of an investigation into billing and software problems in Maine. It's also making preparations to bring Canadian hydropower to southern New England.

Hobbins, who worries that Central Maine Power is biting off more than it can chew, said it's smart to invest in improvements that can make the power grid more stable, but he said he wants to make sure that Avangrid is not just focusing on "old thinking and old infrastructure ideas."

Most of all, he said, Avangrid will have to justify why ratepayers should be on the hook.

"They can't expect the ratepayers of Maine, or anyone else in the system, to pick up the tab. The burden will be on them to show what's prudent," he said.