PJM had ordered utilities in the East to reduce voltage to meet the extremely high demand for electricity during the heat wave.
PJM also has canceled its request to consumers to reduce their use of electricity.
The voltage reduction had applied to the Mid-Atlantic region. It affected the service territories of Atlantic City Electric; Baltimore Gas & Electric Co.; Delmarva Power; Jersey Central Power & Light Co. (JCP&L); Metropolitan Edison Co. (Met-Ed); PECO, an Exelon Company; Pepco; Pennsylvania Electric Co. (Penelec); PPL Electric Utilities; PSE&G; and UGI Utilities, Inc.
The 5 percent voltage reduction ended at 5:11 p.m. (EDT) for most of the region and at 6:14 p.m. (EDT) for the Baltimore and Washington areas.
PJM thanked consumers for their conservation of electricity and added that wise use of energy was always prudent. PJM said conservation had been important in meeting power supply needs.