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As a heat wave threatens to strain California’s power supplies, the body that runs the electrical grid for most of the state asked residents to conserve electricity in a statewide Flex Alert.

The California Independent System Operator is calling for residents across the state to voluntary conserve electricity from 3 p.m. to 10 p.m. Thursday.

“With high temperatures in the forecast, the power grid operator is predicting an increase in electricity demand, primarily from air conditioning use,” the ISO said. “Reduced capacity, along with fire activity and heat, has led to a potential shortage of energy supply tomorrow evening.”

A possible electricity shortage is predicted for an hour beginning at 6 p.m. Thursday, officials said.

Parts of California sweltered under record triple-digit temperatures Wednesday, with Camarillo recording 102 degrees, Long Beach seeing 105 degrees and Paso Robles measuring 106 degrees.

The National Weather Service expects another hot day Thursday and possibly more record-breaking temperatures.

Californians are urged to conserve electricity, especially during the late afternoon and early evening, when the grid is “most stressed” because of the higher demand and falling solar energy production, according to ISO.

To reduce demand, residents can set thermostats to 78 degrees or higher and not use appliances during the peak hours.

This would help avoid power interruptions and emergency measures like rotating power outages, officials said.

The grid operator has put out several Flex Alerts in the past few months and there have been major power disruptions this summer.

Here are some more tips for conserving power:

  • Don’t use major appliance use between 3 p.m. and 10 p.m.
  • Turn off unnecessary lights and appliances.
  • Pre-cool your home by running air conditioning at 72 degrees in the morning then turn it up to 78 or higher during the hottest part of the day.
  • Keep windows and doors closed.
  • Unplug phone chargers, power strips without a switch and other equipment when not in use.
  • Turn your water heater down to 120 degrees.
  • Postpone using major appliances like the oven, dishwasher, clothes washer and dryer until cooler times of the day to avoid heating up your home.
  • Run your dishwasher and washing machine only when they’re full, and do it after 10 p.m.
  • Make sure your air conditioner filter is clean — a dirty filter forces the unit to use more energy and could increase costs.