WASHINGTON (BLOOMBERG) - Texas began rolling power blackouts for millions of households for the first time in a decade as an unprecedented Arctic freeze wrought chaos in United States energy markets.

The operator of the state's power grid Ercot ordered network operators to reduce strain on the system as people crank up heaters to try and keep warm. About 10.5 gigawatts of demand was reduced, equivalent to two million homes. Supplies are scarce, as the extreme weather conditions have caused 30 gigawatts of generation to halt.

"Every grid operator and every electric company is fighting to restore power right now," Ercot president and chief executive officer Bill Magness said.

These are the first mandated blackouts during winter since 2011 when a similar bout of freezing weather knocked out swathes of generating units. Spikes in electricity demand usually happen in summer in Texas when air-conditioning use rises. The extreme cold has caught the energy industry off guard and the system is failing to cope.

Rotating outages will likely last throughout Monday (Feb 15) morning and are a possibility until the weather weather conditions ease, Ercot said in a statement. Power to residential neighbourhoods and small businesses is expected to be cut for up to 45 minutes at a time. In Houston, the city's main utility said that most customers there would be impacted, with outages possibly lasting more than an hour.

About 800 daily records for cold temperatures have been set in the past week as Arctic air pushes all the way to the Gulf of Mexico, sending shockwaves through energy markets. Winter storm warnings, advisories and watches stretch from New Mexico to Maine, with temperatures in Fargo, North Dakota, dropping to about minus 18 Fahrenheit (minus 28 degrees Celsius) early on Monday.

Frigid temperatures and a parade of storms in the US follow other instances of extreme winter weather this year that have snarled ports and upended energy markets in Asia and Europe. Texas, which isn't accustomed to winter's full fury, is getting a big taste. President Joe Biden declared a state of emergency, mobilising federal assistance to aid local response efforts.

Record demand

Ercot is expecting power demand to hit an all-time high on Monday and Tuesday, breaking a record set during a summer heatwave in 2019.

"We would expect to be in emergency operations tomorrow through at least Tuesday morning," said Mr Dan Woodfin, a senior director at Ercot.

The power crunch is being compounded by a lack of wind generation to help ease the load with output, almost halving to 5.1 gigawatts from earlier. Wind turbines may freeze in bitterly cold weather, reducing efficiency, and the blades can ultimately stopping spinning.

The Arctic blast is threatening to crimp crude supplies and unleash a rush for everything from propane to heating oil, fuels that are used in mobile heating devices.

Odessa, one of the largest oil producing areas in the Permian Basin, still has power. While San Antonio has lost power with rolling blackouts lasting 10-15 minutes, according to sources on the ground.

In Houston, there are long lines to refill household propane canisters and firewood is selling out. The city may pick up as much as 2 inches (5cm) of snow overnight, along with ice and sleet, the National Weather Service said. It will get hit by another storm bringing ice and freezing rain on Wednesday.

The Dallas-Fort Worth area could get from 4 to 6 inches (10cm to 15cm) of snow overnight. More snow could follow on Wednesday.

"It is going to be a cold week," said Mr David Roth, a senior branch forecaster at the US Weather Prediction Centre. "The southern plains are in a cold pattern and it is going to take a while for them to break out of it."

Frozen turbines

A mix of freezing temperatures and precipitation threatens to paralyse wind farms in Texas. That would be devastating for power plants with contracts to provide a certain amount of electricity at specific times if they need to instead buy it on the spot market to meet their obligations. At the moment, that power is exceedingly expensive.

"When wind turbine blades get covered with ice, they need to be shut down," said Mr Joshua Rhodes, a research associate who focuses on energy at the University of Texas at Austin.

About half of Texas' wind turbines were inoperable on Sunday morning because of ice and cold. Yet those that are running are cranking out more power than forecast for this time of year, Ercot's Mr Woodfin said during a briefing.

The storms will largely miss major cities along the East Coast, Mr Bob Oravec, senior branch forecaster with the US Weather Prediction Centre said. While there could be some snow showers and ice in New York and Boston, the bulk of the accumulation will be in upstate New York and interior New England on Monday to Tuesday.