Every summer someone shares the tip about turning your air conditioner completely off when you leave the house. In a mild climate, that's reasonable advice. In San Antonio in July, it can backfire — and understanding why will save you more than any single setting change.
Here's the problem. When you shut the system off entirely on a 100-degree day, your house doesn't just get warm — the walls, floors, furniture, and framing all absorb heat. When you come home and drop the thermostat, the system has to pull heat back out of all that mass, not just the air. It runs for hours at full load during the hottest, most expensive part of the day, and it struggles to dehumidify while doing it.
A setback works better than a shutdown. Raising the thermostat 4 to 7 degrees while you're out captures most of the savings without letting the house become a heat sink. For most San Antonio homes, that means around 78 degrees when you're home and 82 to 85 while you're away — not 90 with the system off.
Program the recovery, don't chase it. A programmable or smart thermostat that begins cooling 30 to 60 minutes before you arrive lets the system do that work gradually rather than at maximum load. Smart thermostats that learn your home's recovery time handle this automatically, and that feature is worth more in Texas than almost anywhere else.
Leave the fan on AUTO, not ON. Running the blower continuously feels like it should help circulation, but during humid weather it re-evaporates moisture off the coil and pushes it back into your house between cooling cycles. Your home ends up feeling clammy at the same temperature, and clammy air makes people reach for a lower setpoint.
One more thing worth checking: where your thermostat actually is. A thermostat on a wall that gets afternoon sun, or above a lamp, or near a supply vent, reads a temperature your house isn't experiencing. It will short-cycle the system or run it far too long. If your thermostat is in a bad location, relocating it does more than any setting you could program into it.
Not sure whether your system is performing the way it should at the settings you're using? BB&M AC and Heating will measure it and tell you honestly. Call (210) 876-7140.