As of late September 2026, summer still isn’t finished with Riverside, and my old ranch house holds the afternoon heat well into the evening. My heat-wave routine for years went like this: the house sits closed up all day while I’m out, I walk in around five, and I push the thermostat down as far as it will go. The house is hottest when I get home, so that’s when it needs the AC. That was my whole logic.
Riverside Public Utilities explains on its Flex Alert page that the California Independent System Operator issues these alerts, typically in summer when extreme heat pushes up demand, and that a Flex Alert is “a call for consumers to voluntarily conserve electricity when there is a predicted shortage of energy supply.” Its advice on saving energy and staying cool includes the thermostat: 78° or higher during peak hours. And the city has seen the peak up close. In a Sept. 8, 2022 release, the utility said average hourly usage hit a record 648 megawatts between 3 and 4 p.m. on a day when temperatures soared to 106 degrees, and passed along the state’s advice to pre-cool homes before 4 p.m.
Have an HVAC pro set up pre-cooling.You describe wanting the house pre-cooled before the afternoon peak and held at 78, and local HVAC pros call about the job.“I want my AC to pre-cool the house before the afternoon peak.”→Free for homeowners · Your number stays private
What the California Public Utilities Commission says
The California Public Utilities Commission oversees the Flex Alert program here in California, and it says Flex Alerts are most common during extreme heat events, particularly in the late afternoon and evening, when energy use remains high and solar energy production declines. Its advice for an alert day includes what to do before 4 p.m.: “Pre-cool your home for the evening by running your air conditioning during the day, when more clean energy is available.”…