AUSTIN (KXAN) — Downed trees and ice on power lines left tens of thousands of people in Austin in the dark on Wednesday. At times, nearly a third of Austin Energy’s customers faced outages, from hospitals to houses.

Austin Energy has to prioritize its response when faced with this many outages, a spokesperson explained, but several factors will affect which outages get addressed first — including whether a “critical infrastructure” customer is affected, how many people are impacted by a particular outage and how long the power has been out at a location.

Austin Energy spokesperson Matt Mitchell said the power provider was working to get the “greatest number of customers online in the least amount of time.”

Critical infrastructure

So far, all the power outages have been caused by problems on local power lines and not a result of forced outages or rolling blackouts, as were seen in the February 2021 storm — when tight conditions on the statewide power grid forced the grid operator, ERCOT, to ask power providers like Austin Energy to manually take their customers offline, in order to avoid a statewide catastrophe.

At the time, KXAN investigators discovered Austin Energy keeps track of which of its electric circuits contain critical infrastructure. It also categorizes these organizations into different tiers.

Tier One circuits serve area hospitals, 911 or telecommunication centers, the airport, water treatment plants, wastewater plants and — because of the way the system is set up — any of the nearby homes or businesses that share the circuit.

Tier Two circuits contain places such as nursing homes, detention facilities and ambulatory clinics. Austin Energy did not detail a full list of critical infrastructure, for safety reasons.

During a forced outage event, such as in 2021, Austin Energy said it does everything it can to avoid shutting off power to critical infrastructure.

However, this designation does not guarantee these locations will keep their lights on. Localized outages caused by ice or tree limbs on power lines can still affect power at these locations during a winter weather event, as has been seen during this most recent ice storm.

Mitchell told KXAN investigators Wednesday that Austin Energy crews were prioritizing power restoration at places designated as critical infrastructure.

For example, St. David’s North Austin Medical Center experienced an outage Wednesday morning, according to a statement from the hospital’s CEO Tom Jackson. He said the hospital only lost power “briefly” but that power had since been restored. He noted the hospital also has generators to provide an alternative source of power.

In a statement to KXAN, Jackson said, in part, “the safety of our patients was not compromised at any time. In an abundance of caution, all remaining non-emergent procedures are being rescheduled.”

Ascension Seton confirmed to KXAN its Northwest location was also operating on backup generators Wednesday afternoon after an outage.

Other factors

After addressing critical infrastructure, Austin Energy triages outages based on the impact to the community.

Mitchell said it works on restoring the largest outages first, as well as “the oldest to the newest.”

He explained that its crews also have to consider the length of time a particular repair will take. For example, a fallen power line and a blown transformer require different types of repairs.

“Each outage is a complex event,” he explained. “The crews on the scene must locate and assess the cause of the outage and communicate with other crews and the control center, often during changing conditions such as darkness, wind, rain, and flooding.”

He noted that crews must drive to each repair location, which can often mean hundreds of different trips.

“We strive to restore power to our customers as safely, quickly and efficiently as possible. This work is often quite hazardous. We place the highest priority on the safety of our crews and our customers,” Mitchell said.

As of 4 p.m. on Wednesday, Austin Energy reported 798 unique outages affecting more than 170,000 customers.