Sargent, the highest-paid public servant on the city's payroll, served in a volunteer role on ERCOT, representing the municipal segment of the state's power market.
In her resignation letter, Sargent said the state's power community needs to work together to ensure accountability for the power outages that devastated Texas in mid-February and left millions of Texans and hundreds of thousands of Austinites without power for days.
"I am heartened that our industry intends to take a tough look at recent events and make necessary changes, and I believe my resignation will allow me to more fully support those efforts," Sargent wrote.
With Sargent's resignation, more than half of the ERCOT board's seats are vacant. The board of directors voted to terminate CEO Bill Magness on March 3. The agency's chair and vice chair also stepped down immediately following the blackouts, as did three other members and another prospective board member who applied to fill a vacancy. DeAnn Walker, chair of the Texas Public Utility Commission, also stepped down from her role leading the governor-appointed agency that oversees ERCOT as she faced mounting pressure from lawmakers to resign.