HOUSTON, Dec 9 (Reuters) - Freezing weather across Texas set two December power use records over the weekend as residents worked to stay warm, according to preliminary data from the state's power grid operator.
Power demand on Friday reached 51,484 megawatts in the hour ending at 7 p.m. CDT (0100 GMT), surpassing the December 2011 record of 50,100 MW, according to the website for the Electric Reliability Council of Texas (ERCOT), the state's primary grid.
On Saturday, that record fell as power consumption rose to 52,279 MW at 7 p.m., up 4 percent from the 2011 record.
ERCOT has now recorded the third monthly power demand record this year.
Electricity use in Texas has been growing faster than generation is being built, shrinking the region's reserve margin and increasing the prospect of rolling outages when supplies are stretched, the grid operator has warned.
Over the weekend, a winter storm barreled as far south as Texas, paring 20 to 35 degrees Fahrenheit from normal high temperatures in Houston, San Antonio and Dallas, Texas' largest cities.
An ice storm covering much of North Texas kept temperatures below freezing (0 degrees Celsius) from Thursday night into Sunday, according to AccuWeather.com.
Monday's high in Dallas is forecast to reach 36 degrees F, 20 degrees colder than normal. The city's low will be 24, 15 degrees F below normal, AccuWeather.com said.
A slow warming trend is forecast for the state through the week, paring electric use, according to ERCOT forecasts.
Real-time power prices in the state indicated ample power supplies were available over the weekend.
Texas normally sees peak cold-weather power demand in January or February. December's record power demand has surpassed the grid agency's winter forecast of less than 50,000 MW under normal weather conditions.
ERCOT has set three straight monthly power records.
On Nov. 25, power use reached 46,931 MW, surpassing a November 2006 record of 45,143 MW.
Power use in October reached 54,710 MW, beating the 54,102 MW record set in 2002, according to ERCOT's website.
ERCOT's winter consumption record is 57,265 MW set on Feb. 10, 2011 during an extreme statewide cold spell. The state's all-time peak use of 68,379 MW occurred in August of the same year during a prolonged heat wave and drought.
One megawatt can power about 500 homes during mild weather conditions and about 200 homes during high-demand summer months, ERCOT said.
Power producers in Texas include Luminant, a unit of privately held Energy Future Holdings, NRG Energy , Calpine Corp, NextEra Energy and Exelon Corp.