The resignation letters were filed with the state's Public Utility Commission, which oversees the Electric Reliability Council of Texas, on Tuesday afternoon:
The directors stepping down are Chairwoman Sally Talberg, Vice Chairman Peter Cramton, Committee Chairman Terry Bulger, and Committee Chairman Raymond Hepper. They are "unaffiliated" directors, which means they must remain independent of business ERCOT oversees, according to the Texas Tribune. The fifth board member leaving is Vanessa Anesetti-Parra.
All of them live outside of Texas, which has only intensified criticism of ERCOT.
During a Board of Directors Meeting on Wednesday, Talberg said that the Independent Retail Electric Provider Segment Alternate had also resigned on Tuesday.
ERCOT drew blame for the way it handled the major power outage during the dangerous winter weather that claimed at least 80 lives.
More than 4 million Texans were reported without power last week, despite the rotating outages initiated by the operator.
Sixteen members serve on the ERCOT board, including the four unaffiliated directors whose resignations will be effective at the end of the meeting Wednesday. The vacancies will not immediately be filled, according to the Texas Tribune.
The resignations also come a day before Texas lawmakers are set to begin hearings over the outages.
Texas Governor Greg Abbott, who has been very vocal in his criticism of the board, declared the reform of ERCOT an emergency item this legislative session in the hopes of getting to the bottom of what happened and ensuring it doesn't happen again.
The governor released the following statement in response to the resignations:
"When Texans were in desperate need of electricity, ERCOT failed to do its job and Texans were left shivering in their homes without power. ERCOT leadership made assurances that Texas’ power infrastructure was prepared for the winter storm, but those assurances proved to be devastatingly false. The lack of preparedness and transparency at ERCOT is unacceptable, and I welcome these resignations. The State of Texas will continue to investigate ERCOT and uncover the full picture of what went wrong, and we will ensure that the disastrous events of last week are never repeated."
ERCOT released the following statement regarding the resignations:
"We look forward to working with the Texas Legislature, and we thank the outgoing Board Members for their service."
ERCOT manages the flow of electric power to more than 26 million Texas customers, representing about 90% of the state's electric load.
As the sole operator for the region, ERCOT schedules power on an electric grid that connects more than 46,500 miles of transmission lines and more than 680 generation units.
The Associated Press and The Texas Tribune contributed to this report.