As of late September 2026, the swamp cooler on my old ranch house here in Riverside still runs most afternoons. For years my habit was the one I still see on my street: switch the cooler on, then shut every window and door tight, the way you would with central air. A sealed house holds the cool in. That was my thinking, and it was backwards.
Riverside Public Utilities puts these coolers on its rebate table, whole-house units and wall or window units both, so the city’s own utility pays people here in California to put them in. The rebate table is about buying one; the windows are up to you.
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What the Department of Energy says
The Department of Energy’s page on evaporative coolers says it in the section on how they work: “When operating an evaporative cooler, windows are partially opened to allow warm indoor air to escape as it is replaced by cooler air.” That isn’t tucked into a list of extras. It’s how the cooler is described working…