AUGUSTA – Mainers will have to pay $300 million more for electricity over the next four years under a decision the Federal Energy Regulatory Commission announced Thursday.

Gov. John Baldacci said the state will fight the “unbelievable” decision.

The pricing plan FERC approved is designed to provide funds to build new power plants to meet New England’s growing electricity needs.

“They are talking about a 6 or 7 percent increase, and that is unacceptable,” Baldacci said. “We’re fighting this, and we are going to be utilizing our congressional delegation at the same time we are going to be looking at alternatives.”

Lawmakers approved legislation Baldacci submitted earlier this year that directs the Public Utilities Commission to study whether Maine should continue as a member of the New England Power Pool or ISO-New England, the Independent System Operator for the region.

“We have to look at alternatives and we are looking at them,” he said. “We are moving forward on exploring our options.”

PUC Chairman Kurt Adams said the study ordered by the Legislature is under way. He joined Baldacci in expressing concern over the FERC decision that he said would broadly affect Mainers.

“The companies that are going to get these additional payments are already making record profits,” he said. “It’s incomprehensible.”

In a statement, FERC Commission Chairman Joseph T. Kelliher defended the decision. He said there need to be investments in new generating and distribution facilities in New England and that will not occur without increased costs to ratepayers.

“Our decision today is not without controversy, and I am sure it will be criticized by some in the region,” he said. “In the end, I would prefer to be criticized for acting to prevent a crisis – a crisis that New England knows is coming – than be criticized for failing to act responsibly.”

The FERC ruling sets up a new system whereby power generators will be able to bid for the right to build power plants, transmission lines and supply electricity to companies that distribute power such as Central Maine Power Co. and Bangor Hydro-Electric Co.

Adams said the actual FERC order would not be available until next week, so he is not certain how the new auction system would work and what its full impact could be on Maine.

He did agree there are capacity needs in New England, but argued that the improvements should be paid for by those that will benefit from the improvements. He said the FERC action is aimed at improving capacity in parts of Connecticut and Massachusetts.

“We’ve got plenty of capacity in Maine,” he said, “We are not part of the problem.”

The issue has been simmering for a year. Adams was so angry with discussions last January that he walked out of a meeting called to negotiate a settlement among the 115 parties to the FERC proceeding. Maine was one of eight parties rejecting the proposed settlement.

According to ISO-New England, the FERC-approved plan would have a four-year transition period beginning Dec. 1, 2006. Over that period, the most that would be paid by ratepayers in the region would be $4.8 billion to operate existing generating plants.

The auction program would start in 2008, but the first payments due from the bids would not be until 2010. Ratepayers across New England would pay for the transition period in higher rates.

The Maine PUC estimates that state residential customers would see increases of 6 percent starting Dec. 1. The increase for medium and large commercial and industrial electric consumers will be about 10 percent.

“Another increase on top of the increase we just got, that is not good news for business,” said David Clough, Maine director of the National Federation of Independent Businesses. “We just saw increases this spring. We are already a high energy-cost state.”

When appeals might be filed and when there might be legislation to pull Maine from ISO-New England is unclear. Adams said he does not have authority on his own to appeal the FERC decision.

“The commission will have to meet in open session and deliberate on whether to appeal,” Adams said. “The governor is not as constrained as we are.”

Baldacci can order the state Public Advocate to appeal the FERC ruling whether the PUC appeals or not.

As for replacing ISO-New England, Baldacci said he hopes to have legislation establishing an alternative group, possibly including one or more Canadian provinces, ready for lawmakers in January. Lawmakers reserved the right to decide whether to continue membership in ISO-New England in the study measure

“If we have an agreement sooner, yes, I would consider calling them [the Legislature] back,” Baldacci said.

Adams said reaching a deal would be time-consuming but said the PUC would “make every effort” to have a plan ready for lawmakers to consider in January.