Power outages intensified in Louisiana and Mississippi as conditions from a historic winter storm curbed the region's supply just as demand rose.
Texas' problems also spread, with water supply now in jeopardy after thousands of pipes burst. Officials are urging Texans to boil tap water for drinking.
Texas Gov. Greg Abbott signed an executive order Wednesday night directing natural gas providers to stop any shipments outside the state.
More than 560,000 customers in Texas were without power Thursday, according to data from PowerOutage.us. The new numbers do represent progress — at one point on Tuesday more than 4 million customers had no power — but for some it's now been multiple days of frigid conditions with no heat.
More than 100,000 customers were without power in Louisiana, while nearly 200,000 customers have been impacted in Mississippi, PowerOutage.us found.
"We do our best to plan for events, but I mean this is beyond anything that I believe any reasonable person would have said would have happened at the same time," Joshua Rhodes, research associate at the University of Texas at Austin, said Thursday on CNBC's "Worldwide Exchange." "It is somewhat of the perfect storm."
Wintery conditions affected power production from natural gas, coal, renewables and other sources, just as consumers turned up their thermostats amid frigid temperatures. The grid couldn't match supply and demand dynamics, and had to shut off power for millions of customers.
An estimated 3 million barrels per day of oil production remained offline. At least a fifth of U.S. refining output has been shut. Some are simply too cold to operate, while others cannot receive delivery because of frozen pipelines or other problems.
Energy prices started Thursday in the green, but gave back some of their recent gains as the day wore on. Natural gas shed 4.8%, but is still roughly 5% higher for the week. West Texas Intermediate crude futures rose to a session high of $62.26 per barrel, the highest level in 13 months, before ultimately closing 1% lower at $60.52 per barrel. Gasoline futures hit a high of $1.8486, the highest level since July 2019, during Thursday's session.
"Unprecedented price spikes in power and natural gas, with other energy commodities also reacting, highlight domino effects across markets," Citi analysts said.
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