Additional rolling outages possible late Wednesday or early Thursday.

While the Electric Reliability Council of Texas (ERCOT) discontinued the requirement to shed load across the state at around 2 p.m. on Wednesday, utilities were advised to be prepared for a possible repeat of today’s power emergency later tonight or early tomorrow. Conservation remains critical and customers are urged to reduce demand as much as possible.

Approximately 4,500 CPS Energy customers were reported to be without power as of 3:30 p.m. Outage numbers are expected to increase in the early evening, as customers return home from work to find they are without electricity.

Customers who experience outages are encouraged to report problems to the CPS Energy call center at 353-4357 (HELP), turn off major appliances, especially electric heaters, so that when the power is restored, their CPS Energy circuits are not tripped by the heavy load demand—causing additional, longer outages.

The ERCOT power emergency began shortly before 6 a.m. Wednesday and by 8 a.m., about 70,000 San Antonio customers were without power.  CPS Energy initially anticipated rolling outages would last about 15 to 20 minutes, but as ERCOT increased the amount of energy that had to be dropped to 4,000 megawatts (MW), CPS Energy had to leave some customers without power for as long as an hour.  Additionally, some normal outages—those not caused by the state-wide outage requirement—lasted up to five hours during the same period.

In addition to implementing rolling outages as needed, CPS Energy also brought additional power plants online to help meet the high statewide demand for electricity. Those plants are expected to remain online throughout the duration of the weather incident.

The power shortage was a result of a spike in electricity demand at a time when multiple plants across the state were offline for maintenance and others were experiencing weather-related interruptions in service. Early in the morning, CPS Energy’s J.K. Spruce Unit 2 went offline but was returned to service by 11 a.m.

One success came in the form of larger CPS Energy customers who are part of demand response programs to voluntarily shed load, reducing local demand by almost 50 MW during the ERCOT power emergency. Participating customers included CitiCorp, CVS/Caremark, Johnson Controls, Lowe’s, Matheson Tri-Gas, Microsoft and Valero.

ERCOT has not yet determined whether additional rolling outages could be required later tonight or tomorrow, as electric demand increases when temperatures drop into the teens state-wide.

CPS Energy will continue to provide updates online and via Facebook and Twitter as information becomes available.