PORTLAND – Central Maine Power is proposing another reduction in its delivery rates that would offset increases that residential customers saw on their bills effective March 1.

Last month’s 2.4 percent overall rate increase would have been greater if CMP had not already reduced its portion of the bill by 7 percent. Now CMP is proposing further reducing its rates by 5.5 percent.

About two-thirds of each customer’s monthly bill covers CMP’s transmission and distribution costs and the rest pays for generation of electricity.

CMP’s proposal would bring the overall bill for residential customers down to the level before the March 1 rate increase. If it is approved, it would mean a 22 percent drop in CMP’s delivery costs since the electric utility industry in Maine was deregulated.

The request is under review at the Maine Public Utilities Commission. The commission is expected to make a decision by late next month, allowing it to go into effect on July 1, said spokesman Phil Lindley.