The contiguous United States’ electrical power grid is separated into three parts: Two make up the Eastern Interconnection and the Western Interconnection, and their grids power both sides of the lower 48 states.
The third grid — called the Electric Reliability Council of Texas — is an electrical island that powers Texas, and it remains separate from the other two.
A reader asked Curious Texas: How did Texas wind up on its own electrical grid?
Texas has always operated on its own power grid, but the main motivator was the federal government, said former ERCOT president and CEO Bill Magness.
Regional utilities in Texas created limited connections during World War II when the war effort demanded large amounts of power be sent to the Gulf Coast. The connections enabled power to flow from all over Texas to where it was needed most. That grid became the Texas Interconnected System.
In 1935, President Franklin D. Roosevelt signed the Federal Power Act, which gave the federal government the authority to regulate interstate power lines. Texas, having created its own grid, decided it wanted no part of the act.
“These entities decided that they wanted to keep their power flows intrastate,” Magness said. “They wanted to keep them all in Texas so they wouldn’t be subject to this new federal power over electricity.”
ERCOT was formed in 1970, after a major blackout in the Northeast in November 1965.
The agency was asked to manage a regional electric reliability council in accordance with national standards. ERCOT remains out of the jurisdiction of the Federal Energy Regulatory Commission, but it still has to adhere to North American Electric Reliability Corporation reliability standards.
The power grid doesn’t actually cover the entire state, Magness said. ERCOT manages about 75% of Texas’ land area and powers roughly 90% of its residents. Not included are El Paso, parts of northeast Texas (Longview, Marshall and Texarkana) and parts of southeast Texas (Beaumont, Port Arthur and The Woodlands).
Although ERCOT remains isolated, there have been some exceptions to help maintain control of the flow of electricity.
ERCOT has four direct current ties to other grids: two are in the northeastern parts of the state with about 820 megawatts flowing between the grids, and the other two direct current ties are connected to Mexico — one in Laredo at 100 megawatts and the other in McAllen at 300 megawatts.
Magness said the connections in Mexico are minor compared to how much electricity Texans typically use. On a summer day, the demand is well over 74,000 megawatts, he said.
“It’s kind of a drop in the bucket, but there are those minor connections,” Magness said. “That aside, we do operate electrically as an island.”
An event known as the “Midnight Connection” occurred in 1976 after a Texas utility flipped a switch and allowed power to flow to one of its properties in Oklahoma for a few hours. Once that switch was flipped, Texas became subject to federal jurisdiction, setting off a major legal battle that lasted years.
Compromises were struck and Texas remained free from the oversight of the federal government, but it also created those limited direct currents ties to other grids that cross state lines that aren’t subject to the Federal Power Act.