RIVERSIDE, Calif. (CNS) — Managers of California's power grid were anticipating another day of high electricity demand Saturday, one day after initiating rolling blackouts for the first time since 2001.

After a day that saw triple-digit temperatures in many parts of the state, the California Independent System Operator declared a Stage 3 Emergency at 8 p.m. Friday and directed utility companies to initiate rotating outages throughout California.

Southern California Edison announced at 7:45 p.m. that it had been instructed to begin rotating, one-hour service interruptions. Shortly after, Riverside Public Utilities tweeted that "rotating outages may occur to maintain statewide grid stability."

The Imperial Irrigation District, which services parts of the Coachella Valley, including Indio, did not announce any rolling blackouts, but did ask customers to conserve energy.

"While the district has been able to meet customer energy demand, we'd like to encourage customers to take some easy energy-saving measures during this time that can keep costs down and help maintain the reliability of the electric grid,'' IID Energy Manager Marilyn del Bosque Gilbert said.

The emergency was lifted shortly before 10 p.m., and power was restored. 

"A Stage 3 Emergency is declared when demand outpaces available supply," Cal-ISO said in a statement. The order was declared after "extreme heat drove up electricity demand across California, causing the ISO to dip into its operating reserves for supply to cover demand."

"Although a Stage Emergency is a significant inconvenience to those affected by rotating power interruptions, it is preferable to manage an emergency with controlled measures rather than let it cause widespread and more prolonged disruption," Cal-ISO said.

A Flex Alert was issued earlier in the day, urging residents statewide to conserve electricity between 3 and 10 p.m. to avoid overloading the power system.

Energy conservation tips from ISO include the following:

• Turn off unnecessary lights
• Use major appliances before 3 p.m. and after 10 p.m.
• Set air conditioner thermostats to 78 degrees or higher
• Use electric fans instead of air conditioning when practical
• Keep drapes drawn
• Limit the opening and reopening of refrigerators, which are major users of electricity in many homes
• Operate swimming pool equipment and energy-intensive appliances, such as dishwashers, washing machines, and dryers, during early-morning and late-evening hours

According to CAL-ISO, the state's available capacity for Saturday was hovering slightly above 50,000 megawatts, with peak demand expected to be 46,372 megawatts.