Sweat poured down lineman Scott Graff’s face and beard as he quickly worked Thursday morning to replace a nearly 20-year-old Dominion Virginia Power 15-kilovolt-amp transformer that provides electricity to six homes in North Arlington. Temperatures were already topping 90 degrees.

Graff and Matt Allen, a Dominion ground man, replace about eight transformers a week as part of the utility’s $20 million Neighborhood Transformer Replacement Program. The project identifies transformers that are overloaded and replaces them with new ones that can handle the higher loads coming from surging air conditioners, big-screen televisions and charging cellphones.

Despite the heat, the replacements will continue through the week because “whatever we don’t do planned, we will have to do as an emergency,” said Le-Ha Anderson, a Dominion spokesperson.

Planned outages can last 90 minutes. An emergency fix could take up to eight hours, she said.

“I can remember in heat like this, we’d load up a trailer [with transformers] and go from job site to job site” replacing blown equipment, said Tim Bradley, a Dominion construction supervisor, recalling his time as a lineman.

About 700 transformers have been replaced in the two-year project, which covers Northern Virginia, Richmond and Hampton Roads, and 1,400 more will be.

More than 200, affecting 7,500 customers, have been replaced in older neighborhoods in Arlington, Alexandria, McLean, Falls Church and Springfield, and about 500 more in those areas are slated for the upgrades.

Electric utilities across the region were prepared for the weather, officials said.

Pepco, which serves 778,000 customers in the District, Montgomery and Prince George’s counties, performed maintenance and checked equipment at its substations to prepare for the summer months, said Bob Hainey, a Pepco spokesman.

The utility received assurances from PJM Interconnection, which coordinates regional electricity movement and consumption, that “we’ve got enough power to handle” the heat wave, Hainey said.

Linda Foy, a BGE spokeswoman, agreed. She added, “If we do have outages, we want to make sure we limit the duration of those outages” by putting crews out in the field for quick response. BGE serves nearly 300,000 households in Anne Arundel, Calvert, Montgomery and Prince George’s counties.

Electricity usage spikes in the summer months because of air conditioning. But the power system also has to deal with the large number of electronic devices the average home now has. More than 5 percent of homes have installed a second refrigerator in the past 10 years. Sales of big-screen televisions of 46 inches or more have increased 272 percent since 2009.

In Virginia, Dominion crews identify high-usage neighborhoods through load readings and site inspections. Affected customers are notified by letter that an outage will occur, and the crew knocks on doors before doing the work, said Davon Knott, a Dominion construction supervisor.

Allen and Graff said no neighbors near 20th Place North and North Woodstock Street complained to them about the outage Thursday morning.

Within 45 minutes, Graff and Allen had replaced the rusted, worn transformer with one with twice the capacity and had the power back on. The new transformer has animal guards and an extra fuse that helps protect against power surges and lightening strikes.

Graff lowered the bucket he was standing in and dumped the sweat out of his rubber gloves. He quickly removed his protective rubber sleeves and drank down the bottle of water Allen handed him. It was the first ounces of the gallon and a half or more he said he would drink Thursday.

Dominion Virginia Power serves 2.4 million customers statewide. Of those, more than 900,000 are in Northern Virginia. The replacement project is part of the utility’s $1.7 billion in reliability projects.