Last modified: Tuesday, July 7, 2009 2:21 AM EDT Watch for electric bill shock BY SUN CHRONICLE STAFF Many Attleboro area residents could soon be paying more for electricity. National Grid, which supplies power to Attleboro, Foxboro, Norton, Plainville, Rehoboth, Seekonk and Wrentham, wants to raise rates that would result in a 5.5 percent increase in the typical residential customer's monthly bill. The largest electric utility in Massachusetts wants to use the extra $111 million in revenue to upgrade its electrical distribution system and cover a large amount of unpaid customers bills. AG Coakley opposes hike Attorney General Martha Coakley opposes the hike, calling them "excessive and harmful" to customers. The state Department of Public Utilities is hosting a series of public hearings this week on proposed rate hikes. The first public hearing is this evening at Nantucket High School. Subsequent hearings will be held in Worcester, Andover, Quincy and North Adams.