By Jimmy Vielkind

New York City's electric utility is preparing for new strains on the grid this summer as people who normally commute to work stay home as a result of the new coronavirus.

Consolidated Edison Inc. bought a dozen mobile generators and has made targeted upgrades in areas of Brooklyn where the power went out last summer, executives said at a recent hearing.

"This has never been done," Patrick McHugh, Con Ed's vice president for engineering and planning, told members of the New York City Council last month. The utility normally prepares for higher usage in the warmer months, but has never before faced such a shift in demand.

Residential customers are already using more electricity as they shelter in place during the coronavirus pandemic. A Columbia University study of energy consumption in 400 city apartments during the second full week after New York's stay-home order took effect March 22 found weekday usage increased by 7%, and usage in the middle of the day was 23% higher than the preceding weeks.

However, Con Ed projects its peak demand this summer will be 10% lower than normal because businesses that typically use a large share of power -- such as Broadway theaters, and many commercial office buildings -- will either remain closed or lightly occupied.

So far, the pandemic has led to reduced power consumption overall as many businesses closed their doors. The New York Independent System Operator, a clearinghouse that controls the state's power markets, said energy use in the state was 8% to 10% below normal levels during the last two weeks of May, and overall demand was around 15% lower than normal in New York City.

Electricity consumption rises on hot days as people turn on air conditioning units. The NYISO projected the peak demand would be slightly lower than in 2019, and wouldn't be significantly affected by the pandemic.

"It's hard to project where industry will be in New York state and what amount of air conditioning will be on," Wes Yeomans, the NYISO's vice president of operations, said at a recent briefing.

Con Edison said it had invested $1.3 billion to improve reliability and was working closely with city officials to monitor usage. Mr. McHugh said the new usage patterns weren't unlike what is seen on summer weekends, where people are home during afternoon hours that are typically the hottest parts of the day. He did acknowledge a "staycation effect" as some people who otherwise would have left the city remain, potentially driving up demand.

Yury Dvorkin, a professor of electrical and computer engineering at New York University, said it was difficult to predict how demand would shift this summer and noted that the Columbia study took place before warm weather arrived. The city is distributing 74,000 air conditioners to the homes of vulnerable people, which he said could create a strain on the grid.

Dr. Dvorkin said he believed the stress would be focused in residential areas of Manhattan, Brooklyn and Queens. Thousands of New Yorkers in the outer boroughs were without power for as long as two days last summer after high-heat and flooding.

City Councilman Andrew Cohen, a Democrat who represents the northwest Bronx and leads the consumer affairs committee, said he felt reassured by Con Edison's testimony at the hearing but was wary of the utility after last summer's outages.

"If it were somebody else, I would feel more than cautiously optimistic, " Mr. Cohen said. "But based on the testimony, it appears that we're as prepared as we're going to be."

Write to Jimmy Vielkind at Jimmy.Vielkind@wsj.com