The shortage was prompted largely by a near-total loss of wind generation, as well as a failure of several energy providers to reach scheduled production and a spike in electricity usage, the Fort Worth Star-Telegram reported Thursday.
As a result, grid officials immediately went to the second stage of its emergency blackout prevention plan.
"This situation means that there is a heightened risk of ... regular customers being dropped through rotating outages, but that would occur only if further contingencies occur, and only as a last resort to avoid the risk of a complete blackout," the State Operations Center said in an e-mail notice to municipalities.
The Electric Reliability Council of Texas, the quasi-governmental agency that manages the grid, must ensure that power generation and power use remain constantly in balance. Otherwise, the whole grid can go dark, and the result is a systemwide blackout.
According to ERCOT, those interruptible customers who lost power Tuesday night had it restored by 9:40 p.m.. The interruptible customers pay less for electricity in exchange for the agreement that they will let ERCOT cut their power during shortages.
ERCOT reported that wind power production dropped Tuesday evening from about 1,700 megawatts to about 300 megawatts. A single megawatt is enough electricity to power 500 to 700 homes under normal conditions.
The emergency procedures Tuesday night added about 1,100 megawatts to the grid over a 10-minute period, according to ERCOT.
Kent Saathoff, vice president for system operations at ERCOT, said Tuesday's close call demonstrates the challenges of using wind power. Because the wind sometimes stops blowing without a moment's notice, engineers at ERCOT must remain nimble enough to respond to resulting instability on the grid, he said.
"There is a major workshop going on at our office right now to discuss these very issues," Saathoff told the newspaper.
Some critics have said that wind power, although providing a source of clean energy, also brings with it plenty of hidden costs and technical challenges. Besides requiring the construction of expensive transmission lines, the fickle nature of wind also means that the state cannot depend on the turbines to replace other sorts of generators.
Susan Williams Sloan, a spokeswoman for the American Wind Energy Association, said those technical challenges are not insurmountable. She said part of the solution is to locate turbines in diverse areas of the state. "When the wind is not blowing somewhere, it's always blowing somewhere else," she said.
Sloan also said that technological advances will make it easier in the future to forecast wind energy.
About 4,356 megawatts of wind turbines are currently installed in Texas, she said.
