A heat wave has sharply reduced a surplus of electricity in New England as people use more energy to cool down.

more stories like thisThe operator of New England's power grid reported high electricity demand and a tight supply Monday, with expectations of a slightly tighter supply on Tuesday in the six-state region.

Holyoke-based ISO New England Inc. expects to have adequate system capacity including a required power reserve on Tuesday, but the surplus will be much smaller than usual.

The company projects energy use to peak at about 27,000 megawatts on Tuesday, up from nearly 26,000 on Monday. As temperatures cool, the surplus is expected to grow beginning Wednesday. The region's all time peak power use was set Aug. 2, 2006, at 28,130 megawatts.