HOLYOKE, Mass. — With electricity use approaching record levels, New England’s power grid operator asked customers on Tuesday to conserve electricity as a weeklong heat wave continues to bear down on much of the region.

Power is adequate, but supplies are likely to become tight, ISO-New England said.

New England’s electricity use is forecast to reach near record-breaking levels this week as temperatures stay stuck in the mid- to upper-90s. The heat wave is not expected to break until Saturday.

The forecast for the greatest peak demand on Wednesday and Thursday is 27,800 megawatts. Peak demand on Tuesday is forecast at 27,500 megawatts.

The record for electricity use was 28,130 megawatts on Aug. 2, 2006

One megawatt of electricity can power about 1,000 homes.

ISO-New England, based in Holyoke, said conserving electricity is a prudent, precautionary measure to help keep supply and demand in balance. It suggests customers reduce electricity, particularly between noon and 8 p.m.

Customers are advised to raise air conditioning thermostats by a few degrees if health permits to a range of between 74 degrees and 78 degrees, turn off unneeded lights and appliances, unnecessary office equipment, shut off air conditioners when leaving home for extended periods of time and put off using washing machines and dryers.

If more action is required, ISO could call on business customers who have agreed to cut electricity use to conserve power to do so. It can also import more power from grid operators outside the region.

The New York Independent System Operator called for voluntary electricity conservation on Monday, citing sustained high temperatures that could push electricity demand to near record levels. It also asked customers to reduce electricity use.