Arizona Public Service Co. and Tucson Electric Power on Tuesday asked customers to voluntarily reduce how much electricity they use from 3-8 p.m. to prevent blackouts like those in California the past week.
Among the recommendations is to turn thermostats no lower than 80 degrees, turn off unnecessary lights and don’t use big appliances like pool pumps during those hours.
The move comes as California utility customers were told they likely would experience rolling blackouts on Tuesday.
The heat wave in the Southwest has already cooked up the hottest summer on record for Phoenix.
That prompted an Arizona energy regulator on Monday to call for a special meeting to ensure California-style blackouts don’t come to Phoenix.
Such calls for conservation are common in California when hot weather strains the electric grid but haven’t been used by APS since 2004, when a substation burned and reduced the ability to bring electricity to the Phoenix area.
APS officials emphasized that they have enough power resources on hand to prevent rolling blackouts but that the measure was necessary as a precaution.
“We have sufficient supply and reserves,” APS spokesman Jim McDonald said Tuesday.
TEP made similar comments on Twitter in its call for conservation.
“We expect to have enough energy to serve customers, but we’re asking for your help to limit the strain on the grid,” TEP said.
Salt River Project, the Phoenix area’s other major utility, did not call on customers to curtail power usage.
“While SRP continues to encourage our customers to use energy wisely and efficiently manage their bills, we currently have sufficient resources available to meet our customers’ demand,” spokesman Scott Harelson said.
Arizona has plenty of power plants to meet its own customer demand, but the fear Tuesday was that if any of the major power plants were to have a problem, there was not enough “extra” power that could be purchased in the region to take up the slack, said Brad Albert, APS vice president of resource management.
“These decisions are really based on our ability to serve customers reliably,” Albert said “We don’t make these decisions based on being able to come to California’s assistance or something like that.”
He said a similar call for conservation could come Wednesday, based on the weather outlook.
“We will make this decision on a day by day basis,” he said.
All of the nuclear and coal plants supplying APS were operating at or near full capacity Tuesday, he said, and only one minor problem at a gas plant in Yuma and some clouds over solar plants near Prescott were limiting the company’s resources, both by negligible amounts, he said.
APS also had two different programs in effect Tuesday where customers are paid incentives to curtail power during days with high energy demand. One program is for commercial and industrial customers, and another allows the utility to control thermostats for residential customers.
Those programs combined were reducing demand by about 40 megawatts Tuesday, Albert said. That is enough power for about 10,000 homes at once.
While blackouts from storms or accidents are common, those caused by simply not having enough power to supply customers are rare.
The summer of 2004 was the last time APS asked customers to conserve power. Problems began in June when a blue heron’s droppings caused a minor outage on a power line in the West Valley.
A glitch on the power system allowed the problem to spread and forced the shutdown of the Palo Verde Nuclear Generating Station and other power plants that day, and that event damaged a major substation called Westwing.
Westwing then exploded on July 4 that year, reducing power imports to the city by about 20%, forcing officials to ask customers to conserve power for weeks.
The repairs were not complete until the next year.
SRP more recently had to initiate rolling blackouts in 2011 when a hard freeze caused problems across the West, including at multiple power plants the company runs across the state.
The trouble came as coal- and natural-gas-burning power plants in Arizona, New Mexico and Texas faltered with freezing instruments, water lines and other mostly minor issues brought on by the below-freezing temperatures and severe wind-chill factors, a federal report said.
SRP was plagued by issues at six power plants, some operated by other utilities, and had to shut off about 65,000 customers for about an hour.
Reach reporter Ryan Randazzo at firstname.lastname@example.org or 602-444-4331. Follow him on Twitter @UtilityReporter.