AUSTIN (KXAN) — As thousands of people in Austin endure another day without power, Austin Energy leadership explained who gets to keep their lights on and why.

The Electric Reliability Council of Texas ordered energy companies across the state to cut power usage, meaning Austin Energy had to “shed more load” to meet ERCOT’s demands and more Austinites could lose power overnight on Tuesday into Wednesday.

“We are frustrated, but we are working to meet our obligations to maintain the state’s electrical grid,” a tweet from Austin Energy said.

In a news conference on Tuesday night, the company’s general manager noted the consequences statewide, if they don’t.

“There would be a point where the whole system would go black,” Jacqueline Sargent said.

KXAN Investigators have been working to get answers to why some parts of the city never lost power during the storm, while other customers suffered through lengthy cold and dark stretches.

A spokesperson for Austin Energy explained they keep a list of priority, or critical load, customers and make “every effort” to exclude them from rotating outages.  

They explained Tier 1 customers include hospitals, control centers, 911, Austin-Bergstrom International Airport, water and wastewater plants and telecommunications. They noted each of these customers shares a circuit with other commercial and residential customers.

According to Austin Energy, Tier 2 customers include nursing homes, detention centers, ambulatory care clinics and centers, 911 backup and evacuation centers.

“We make every effort not to include Tier 2 customers in rotating outages,” they said, but explained these customers were not exempt from outages in this storm.

There are no businesses included in either Tier 1 or Tier 2 of the critical load list, but some may share a critical load circuit with a Tier 1 or Tier 2 facility, meaning their power could remain on. Austin Energy explained the downtown network provides power to these types of critical loads.

City leaders said in a news conference they were working with the Downtown Austin Alliance to contacted the owners and operators of more than 50 of the largest downtown buildings and construction sites, asking them to turn off lights and help conserve power.