The Public Utilities Commission of Texas has directed an energy monitor to investigate the conditions surrounding the rolling blackouts implemented during last week's weather.

On Feb. 2, CenterPoint Energy started planned, controlled rolling outages following an order from ERCOT to curtail delivery of power to end-use customers in its greater Houston service territory.

CenterPoint Energy said it had pre-determined which circuits/power lines will be systematically brought off-line or curtailed across its entire service territory in order to achieve the load reduction requested by ERCOT. The company's goal was to avoid turning off circuits to facilities vital to safety, health and welfare, such as hospitals, water treatment plants and public service facilities.

Oncor, the electric transmission and distribution company serving most of North Texas, also temporarily turned off power across its service territory to compensate for unexpected generation loss in the areas of the state served by the Electric Reliability Council of Texas. Oncor, which does not own any generation, announced it was taking direction from ERCOT to manage the situation.

The PUC executive director asked the Texas Reliability Entity Inc. — which develops, monitors, assesses and enforces state energy standards — in a letter Feb. 4 to investigate the conditions of the mass emergency electricity shutdown, and whether decisions followed the law.

"You should investigate all the preparations leading to this emergency event, as well as all actions taken once this event occurred," the letter said.