Peco said it came close to a record set in August 2006 that came at the end of a 10-day period of 90-plus degree temperatures, but did not surpass it.
"So far we've had a few days in a row of 90 degree temperatures but, in 2006 when we set our record, we had 10 days of 90, 95, 98 degree weather and that's when you see the record-breaking energy demand," said Peco spokesman Ben Armstrong.
Earlier, Peco worked to restore service to some 8,000 customers.
Officials said the heat put increased load on the power company's systems, blowing fuses at transformers.
Meanwhile, PSE&G said it is continuing to monitor weather conditions, and has extra personnel and supplies on hand for heat-related emergencies.
The peak electric demand is expected to be about 10,500 megawatts, which would be the highest so far this summer.
The company says people should not use unnecessary appliances and should not cool unused parts of the home. They company is also asking customers to wait until later in the day to run washers, dryers and dishwashers.
