U.S. power grid operator PJM Interconnection, the biggest power grid in the nation, said it had enough electricity to keep air conditioners humming as a brutal heat wave blankets its Mid-Atlantic and Midwest region this week.

The grid operator said in a release it does "not expect major problems" even though power usage is expected to top 150,000 megawatts each day this week. That is still well below the grid's all time record of more than 163,000 set in 2011.

One megawatt powers about 1,000 homes in PJM.

PJM however did issue a so-called hot weather alert to its transmission and generation members, asking them to prepare their facilities and workers for the heat and to defer any unnecessary maintenance on transmission equipment and power plants.

PJM issued the hot weather alert to all utilities in its territory except Exelon Corp.'s Commonwealth Edison in Chicago where temperatures are cooler.

PJM operates a grid serving 61 million people in 13 Mid-Atlantic and Midwest states and the District of Columbia.

The biggest power companies in PJM include units of Duke Energy Corp., Exelon, FirstEnergy Corp., American Electric Power Co. Inc., Dominion Resources Inc. and Public Service Enterprise Group Inc.