(Adds context, details on real-time prices and updates demand forecast)
June 20 (Reuters) -
The Texas power grid operator and some utilities on Tuesday called on residents to voluntarily cut back on air conditioning and appliance use as a record-setting heat wave stressed the grid.
Such conservation calls in recent years have become effective tools at avoiding rolling blackouts during periods of high demand. Texas and California avoided rolling blackouts last summer when residents responded to similar calls to lower usage.
The grid operator, Electric Reliability Council of Texas (ERCOT), issued a watch for what it called a "projected reserve capacity shortage" from 3 p.m. to 9 p.m. local time. ERCOT operates the state's grid that covers more than 26 million customers and about 90% of the state's power load.
Although controlled outages are one of the most extreme actions a grid operator could take to maintain reliability, ERCOT said it was not in emergency operations, and controlled outages were not needed.
Extreme weather has been a reminder of the fatal 2021 freeze that left millions of Texans without power, water and heat for days as ERCOT scrambled to prevent a grid collapse when an unusually large amount of generators shut.
AccuWeather forecast temperatures in Houston, the biggest city in Texas, will hit 104 degrees Fahrenheit (40 degrees Celsius) on Tuesday, compared with a normal high of 93 F (34C) for this time of year.
ERCOT forecast power use would reach 81,191 MW on Wednesday. That would top the grid's record peak of 80,148 MW on July 20, 2022.
Day-ahead power prices for Tuesday settled around $2,500 per MWh at 5 p.m. local time in several zones, including Houston and Dallas, according to the ERCOT website.
Real-time power settlement point prices rose above $4,400 per MWh at 1630 CT across all hubs in Texas, according to data from ERCOT.
That compared with next-day prices at the ERCOT North Hub , which includes Dallas, that traded for $37 per MWh for the peak hours during the day on Monday. (Reporting by Seher Dareen, Brijesh Patel and Ashitha Shivaprasad in Bengaluru and Scott DiSavino in New York; Editing by Kim Coghill, Will Dunham, Mark Potter and Deepa Babington)