Thousands of Brooklyn residents were still without power on Monday morning, after Con Ed throttled service in certain neighborhoods amid a searing heat wave and record-shattering energy use on Sunday night.

The outages—which affected roughly 50,000 customers across the region—were concentrated in southeastern Brooklyn, beginning at around sundown last night. Thirty-thousand customers had their power restored overnight, while 13,000 people in Flatbush, Canarsie, Mill Basin and other nearby neighborhoods won't see their lights turned back on until later this afternoon, according to the utility.

Gwendolyn Tucker, a 56-year-old bus driver who lives in Canarsie, said she'd just returned from a work trip to Fort Drum, and was about to turn on the air conditioner and take a bath when the power went out. "We don't have electricity since 6:00, and we still don't," she said. "What're we supposed to do now?"

Tucker ended up spending the night at a friend's place in Bed-Stuy, but said she was worried about older neighbors and families that were stuck in the heat. "A lot of people slept out on their balconies. When I left, everyone was out on their balconies."

The widespread Brooklyn outage comes after last weekend's blackout in Midtown, which knocked out power for 72,000 metered customers (a figure that includes households and businesses, such as venues, apartment buildings, and the entire subway system).

In a briefing on Monday morning, Mayor Bill de Blasio said he was "extremely disappointed" in the utility, which he accused of providing "consistently inconsistent information" about the cause of the service failure. While the situation remained peaceful overnight, the move to cut power just as it was getting dark prompted safety and security concerns, according to the mayor.

In a statement, the company said that they'd made a "preemptive move to take those customers in southeast Brooklyn out of service in order to protect vital equipment and to help restore power as soon as possible." But city officials said they wanted more details from the state-regulated monopoly about how that decision was made.

"We need to know how Con Ed is picking winners and losers in this situation," Councilmember Justin Brannan, who represents Brooklyn's 43rd Council district, told Gothamist. "We're never really told why it happens or what needs to be done so it doesn't happen again. It just keeps happening, and they keep fixing it—like, 'Okay, see you next July!'"

A spokesperson for the company, Allen Drury, said the strategy of intentionally cutting service to spare the power grid happens only in extreme circumstances, and pointed to Hurricane Sandy as an example. In this case, Con Ed customers set an all-time weekend record for peak power usage, reaching a grid-straining 12,063-megawatt load at around 6 p.m. on Sunday. The utility's engineers made the call to black out parts of the borough where equipment was under particular stress, according to Drury.

Earlier in the weekend, Con Ed's president, Tim Cawley, had assured customers that they'd have reliable service during the heat wave, estimating that the system was designed to hold about 13,300 megawatts.

Governor Andrew Cuomo, who floated the idea of revoking Con Ed’s license after last weekend’s blackout, called the situation unacceptable. "We have been through this situation with Con Ed time and again, and they should have been better prepared—period," the governor said in a statement. "This was not a natural disaster; there is no excuse for what has happened in Brooklyn.

Cuomo has for years threatened the utility in the wake of major outages, while stopping short of taking steps to find a new power provider.

With reporting from Gwynne Hogan.