As Texans were waking up to a bone-chilling Monday morning, they cranked up the heat, took hot showers, and sent the state's power grid perilously close to a crisis.
Between 7 and 8 a.m., Texas used 55,486 megawatts of power.
Rolling blackouts were not implemented, but 'we were close,' said Dan Woodfin, the director of systems operations for the Electric Reliability Council of Texas, the agency that operates the state's power grid.
Demand was going up just as two power generating units in North Central Texas were freezing up. They malfunctioned, reducing the amount of power in the state's reserves to a critical low.
ERCOT issued an Energy Emergency Alert (EEA) Level 1 at 6:52 AM, when 2,300 megawatts of electricity remained in the operating reserves.
Just nine minutes later, that number had fallen to 1,750 megawatts. ERCOT issued an EEA 2. At that point, the general public and major corporate partners were asked to conserve.
There's no specific number of megawatts in the reserve that trigger an EEA 3, said ERCOT's Robbie Searcy. An EEA 3 is issued based on when experienced operators believe it's necessary.
On Monday, the reserves reached a low of 1,360 megawatts. Had usage not dropped, and if those malfunctioning units remained inoperative, an EEA 3 would have been issued, triggering rolling blackouts immediately.
As demand for electricity peaked, prices did, too. For about an hour Monday morning, as Texas was shivering, wholesale electricity rates hit the cap, meaning they reached the highest price point allowed by law.
Some companies that buy power and sell it to customers could pass that hike down to consumers who subscribe to variable rate plans.
'What you see is people use more energy, and companies that offer variable rates can make changes to those rates at any time even after somebody's used that power,' explained Juan Elizondo of TXU. TXU does not offer variable plans because of this.
'We think people should know what they're paying. After you've used it, you shouldn't have to pay more for it... it should be up-front and simple,' he said.
A skyrocketing wholesale price was one lesson from 2011, which set a record for peak winter demand of 57,282 megawatts. A realization that many power plants weren't ready for winter weather was another lesson.
Texas suffered rolling blackouts during that frigid February, when about one-quarter of power generating units malfunctioned due to the cold.
ERCOT has since required plants to undergo weatherization updates.
'We've been making site visits to plants that had problems in 2011 to make sure they're implementing the plans,' Woodfin said. 'We had many fewer outages this time as compared to 2011. If we only had a couple plants, that's a vast improvement.'
He did say that some units were unable to produce power due to being offline for other reasons, possibly for maintenance or repair. He said after 2011, changes were made regarding when certain repairs are allowed, but 'it's possible we need to look at that again.'
The EEA 2 remains in effect through Tuesday morning, when ERCOT predicts demand will be at or near the same level it was on Monday. If no power generating unit malfunctions, reserves should be safe.
ERCOT urges electric customers to keep thermostats low and avoid using large appliances between 6 a.m. and 9 a.m. and again between 4 p.m. and 8 p.m.