UNIVERSITY HEIGHTS, The Bronx — Hundreds of families in the west-central Bronx spent all day in Friday’s high heat without electricity for air conditioning or other vital resources. The blackout started around midnight, and lasted well into the afternoon. What frustrated many people the most was that it was a partial power outage — so while most apartments had no electricity, a few did, leaving many neighbors trying to understand how it could happen.

Javier Rodriguez lives in one of the dozen buildings along University Avenue, just south of West Fordham Road.

“It’s hot, and it’s crazy,” he said. “The basement [and] the right side of the building’s got power, and the rest of the building is out.”

Con Edison, which provides electrical service to the Bronx, said that it was a partial blackout. For Ora Gale, who lives in the building next to Rodriguez’s home, a partial outage for the row of buildings is a total blackout.

“One side [of my building] is on, the other side is off,” she said, and added that she lives on the side where the power had been off since midnight.

“We’ve got to get more food,” she added, “because all the food’s got to go into the garbage.”

ConEd has a reimbursement policy for anyone who has to go without power for more than 12 hours during a 24-hour period.

Gales also pointed out, though, that the utility had at first said the electricity would be restored around noon on Friday. But by mid-afternoon, it was still out.

“It’s just horrible,” she said. “I’m going to a hotel.”

Cool water was another, ironic issue related to the power outage. In addition to no electricity for air conditioning, there was no hot water, for bathing or washing. The hot water heaters in most of the affected buildings run on electricity.

As for the cause of the outage, it’s not fully clear, but another resident mentioned how many parts of the Bronx, including here, were inundated on Thursday afternoon.

“There was a big thunderstorm yesterday,” said Calvin Jones. “So we don’t know what to blame.”

A Thursday afternoon thunderstorm knocked out power to about 4,000 Bronx families, whose power Con Ed quickly restored. Those homes are served by overhead power lines. The buildings affected by Friday’s partial blackout are connected to electrical lines that are underground.

Those, according to Con Ed, take much longer for work crews to access and repair.