Heating Chicago buildings

High-rise buildings in Chicago generate steam in the extreme cold. (Alex Garcia, Chicago Tribune / January 7, 2014)

The extreme cold has prompted the organization that operates the electrical grid serving Illinois to ask consumers to turn down the thermostat and avoid using appliances like the stove, dishwasher and laundry machine between 6 a.m. and 9 a.m. and 3 p.m. and 7 p.m.

The frigid weather has led to higher than normal electricity use and the call for conservation during peak hours is an effort to avoid more drastic measures, said a spokeswoman for PJM Interconnection, which coordinates the movement of wholesale electricity to 13 states including Illinois.

The last time the organization asked consumers to take such steps was in summer of 2006 after several days of sustained heat, spokeswoman Paula DuPont-Kidd said.

"This is very rare that we do this," she said.

Voluntary conservation helps electricity providers avoid the need to implement planned outages or voltage reductions. In the present situation, those alternatives are not in play, she said.

"Of course we want people to be warm and not jeopardize their health," she said. "But if they can tolerate the thermostat to be a little lower than normal, every little bit like that reduces the amount of load on the system."

Some commercial and industrial power users like universities, hospitals and supermarkets were asked Tuesday morning to switch to alternative methods, such as back-up generators, for five hours Tuesday, said a spokesman for EnerNOC, which oversees a program designed to curtail energy at times of high use.

Curtailing the load of electricity taken from the grid by dimming lights and shifting production loads to different times of the day helps balance supply and demand during times of high use like during the current cold snap, said Gregg Dixon, an EnerNOC spokesman.

Officials said the possibility of a large-scale power outage low, despite the strain on the electrical supply.

"But we want the public to be aware that … whatever they can do helps," DuPont-Kidd said.

mmanchir@tribune.com | Twitter: @TribuneMM