BOSTON (AP) - State energy regulators have fined three Massachusetts utilities nearly $25 million for their response to two major storms in 2011.

The penalties were announced Tuesday by the Department of Public Utilities after a yearlong investigation.

Some customers were without power for a week after Tropical Storm Irene in August 2011 and a surprise October snowstorm.

By far the biggest penalty was assessed against National Grid, fined $18.7 million. Department of Public Utilities chairwoman Ann Berwick said regulators found "systematic and fundamental failures" in how the company planned for and responded to the storms.

National Grid says in a statement it is reviewing the decision.

NStar was fined $4.1 million and Western Massachusetts Electric Co. was fined $2 million. Both companies, divisions of Hartford, Conn.-based Northeast Utilities, say they plan to appeal.