This story has been updated.

Two months after the worst power crisis in Texas history, the state’s electrical grid operator again warned of tight conditions on the grid, mostly as a result of power generating plants taken offline for maintenance.

The Electric Reliability Council of Texas (ERCOT) called for conservation measures early Tuesday evening, with forecasts for power demand exceeding supply. ERCOT officials said they triggered the conservation alert Tuesday because it allows them to tap into emergency strategies to keep the grid balanced.

ERCOT ended its calls for conservation at 8:45 p.m. after electricity demand dropped off. 

In a call with reporters, ERCOT Vice President Woody Rickerson said ERCOT doesn’t expect Texas residents to see blackouts Tuesday, drawing a contrast between the tight conditions Tuesday and the February winter storm that left more than 4 million households without power and led to more than 200 deaths.

Rickerson primarily blamed power plants that were down for regular spring maintenance ahead of the hot summer months when demand for electricity, also called load, is at its highest.

“It’s really kind of a balancing act of how much maintenance you can allow to get ready for higher-load months and still meet the loads on days like today,” Rickerson said, adding that “today is one of those days when conditions are a little tighter than what we’d like to see.”

Five of CPS Energy’s electricity generating units were offline for maintenance on Tuesday, according to Melissa Sorola, communications director. Those are Spruce 1, a 560-megawatt coal-fired plant; Milton B. Lee East, a 191-megawatt natural gas-fired plant; and the three V.H. Braunig natural gas-fired plants, which add up to 859 megawatts in capacity. One megawatt can power approximately 200 Texas homes on a hot summer day.

At around 5 p.m. when ERCOT called for conservation measures, CPS Energy’s overall supply was 400 megawatts more than its customers’ demand, Chief Customer Engagement Officer Rudy Garza said. CPS Energy makes money when it can sell excess power onto the Texas grid and loses money when it’s forced to buy wholesale power during price spikes.

“It’ll change depending on conditions, but we have enough generally to cover load for this time of year in our service area,” Garza said.

ERCOT also blamed a “stalled cold front” for its faulty electricity demand forecasts, with Rickerson saying that Texas cities didn’t see widespread cooler weather to the degree ERCOT forecasters had predicted.

CPS Energy responded to ERCOT’s call for conservation with a news release and social media posts urging its customers to “reduce their electricity use as much as possible to help prevent electricity emergencies or the need for rotating outages implemented to protect the electric grid.”

Residents should set thermostats 2 to 3 degrees higher, avoid using large appliances, shut off pool pumps between 4 and 6 p.m., and turn off and unplug nonessential appliances. The City also sent a similar alert Tuesday to hundreds of thousands of residents via text.

The emergency calls for conservation come at a time of intense scrutiny of ERCOT, whose CEO resigned along with seven board members in the wake of the winter storm crisis.

Grid-wide, the capacity of the power plants that were offline on Tuesday added up to 32,000 megawatts, Rickerson said – 25% of the total capacity on the ERCOT grid. Most of those plants had planned to stop producing power for routine maintenance.

ERCOT has some control over how many power plants at a given time are down for maintenance, according to Rickerson. Outage requests it receives from power plant operators at least 45 days in advance are accepted automatically, but ERCOT can say no to outage requests submitted less than 45 days in advance.

Rickerson was not able to provide a breakdown Tuesday of how many outages ERCOT had approved and how many had been automatically accepted.

By early Tuesday evening, wholesale electricity prices shot up to the new cap of $2,000 per megawatt-hour across the state. Last month, the Public Utility Commission of Texas, which regulates ERCOT, reduced that cap from $9,000 per megawatt-hour.

CPS Energy is currently suing ERCOT and more than 15 natural gas suppliers over high energy prices during the February storm.

Tight conditions could continue in the weeks ahead, Rickerson said.

“It is a possibility we could have this same phone call again sometime in the next three or four weeks.” Rickerson said.

Brendan Gibbons

Brendan Gibbons is the San Antonio Report's environment and energy reporter.