Will power company merger cost you?

Constellation Energy Group promises its $11.5 merger with FPL Group will benefit customers, but some consumer advocates are expressing doubts.

Florida-based FPL's acquisition of Constellation is the latest example of consolidation within the power industry, a trend that is expected to continue as companies seek to cut costs and balance their portfolios of regulated and unregulated businesses, while diversifying the regions they serve and the fuels they burn.

But as utilities expand, consumer advocates are asking whether local regulators can effectively monitor interstate market activity. They worry that homeowners and...