(Reuters) - Texans' electric use set a new hourly record for June on Tuesday, the second record in as many days, as the state's largest cities baked under triple-digit temperatures.
Power demand reached 65,679 megawatts in the hour between 2 p.m. and 3 p.m. CDT (2000 GMT), surpassing Monday's peak of 65,047 MW, according to preliminary grid data. Tuesday's peak use was on pace to reach 67,000 MW before trending lower this evening.
The early heat wave across the state also pushed demand above the highest hour amount used in any July on record.
Real-time power prices briefly approached $3,000 per megawatt-hour Tuesday afternoon, the current maximum allowed, before dropping back to $1,500.
Houston's high temperature reached 101 degrees Fahrenheit (38 Celsius), 10 degrees above normal, before late afternoon thunderstorms popped up, paring demand.
The heat will begin to wane statewide Wednesday, giving power plants and air conditioners a break.
The state set seven new monthly peak-power records in 2011 as extreme cold in February and an extended heat wave hit the state.
So far, this year, the state has exceeded the 2011 records in May and June.
The state's all-time peak use was 68,379 MW set in August last summer during a protracted heat wave and drought.
The extreme heat hit Sunday when the mercury reached 100 degrees in Houston, San Antonio and Dallas, the three biggest cities in the Lone Star State, prompting residents to crank up air conditioners.
ERCOT and utilities across the state urged residents to limit afternoon power use. The grid agency issued an advisory Tuesday afternoon as supplies tightened, but avoided declaring a power emergency.
The grid agency has projected that power use will peak at 67,492 MW this summer, about 1,300 MW above what would be expected in a normal weather scenario.
One megawatt is enough to serve about 200 Texas homes during hot weather when air conditioners run for extended periods.
ERCOT has warned that rolling outages could occur this summer given the state's limited amount of surplus generation.
An extended heat wave and drought last summer forced ERCOT to declare emergencies on six days and curtail power to interruptible customers on two days in August to avoid widespread rolling outages.
The state's shrinking reserve margin has led regulators to implement a number of wholesale market changes to encourage construction of new power plants over the long-term.
Energy companies have returned several idled power plants to service to bolster the summer supply after a new coal-fired plant expected to be operational was delayed.
The biggest transmission and generation companies in ERCOT include Luminant and Oncor, units of privately held Energy Future Holdings, CenterPoint Energy, American Electric Power, PNM Resources, NRG Energy, Exelon, NextEra Energy and Calpine.
(Reporting by Eileen O'Grady in Houston and Scott DiSavino in New York, editing by Dave Zimmerman and M.D. Golan)