The first truly hot day of the year triggers a reflex for millions of people. As the humidity climbs, you might find yourself cranking the thermostat down to 68 degrees, shutting vents in the guest room, and leaving ceiling fans spinning wildly in every corner of the house.
It feels proactive. It feels like you are fighting back against the heat — and the impending utility bill. But many of these “common sense” strategies are actually financial traps. They don’t just fail to save money; they often increase your energy consumption and wear down your HVAC system faster.
Here are five energy-sucking myths to abandon before the air conditioning season hits full swing.
Myth: Cranking the thermostat down cools your home faster
You walk into a stifling hot house. In a desperate bid for relief, you drop the thermostat to 60 degrees, believing the machine will work harder and faster to reach that target.
The Truth: Your air conditioner is not a gas pedal; it is a light switch. Most central AC systems run at a single speed. They are either on or off. Setting the temperature to 60 degrees produces the same volume of cool air as setting it to 74 degrees. The only difference is that the system will run continuously until it hits that impossible target, wasting electricity long after your home is comfortable.
The Fix: Set the thermostat to your actual desired temperature. If you have a variable-speed unit (which is less common), it acts differently, but for the vast majority of homes, “supercooling” is a waste of energy.
Myth: Ceiling fans cool your rooms
It seems logical to leave ceiling fans running to keep the house cool while you are at work. After all, a moving fan means moving air, which must mean lower temperatures.
The Truth: Fans cool people, not rooms. They work by the wind-chill effect, evaporating moisture on your skin to make you feel cooler. A fan running in an empty room does nothing to lower the actual air temperature. In fact, the motor generates a small amount of heat, potentially warming the room slightly while wasting electricity.
The Fix: Treat fans like lights — turn them off when you leave the room. If you want more ideas to keep your home cool, remember that using fans properly allows you to raise your thermostat setting by about 4 degrees with no reduction in comfort.
Myth: Closing vents in unused rooms saves money
If you aren’t using the guest bedroom, why pay to cool it? Closing the supply vents seems like the ultimate efficiency hack, diverting that precious cold air to the rooms you actually inhabit.
The Truth: Your HVAC system is designed as a balanced loop. When you close vents, you disrupt the pressure balance within the ducts. This increased pressure can force air out through leaks in the ductwork — cooling your attic or crawlspace instead of your living room — or cause the blower motor to work harder, shortening its lifespan. In modern high-efficiency systems, closing too many vents can even freeze the coils or trip safety sensors.
The Fix: Keep supply vents open to ensure proper airflow and system longevity. If you need to zone your home, investigate professional zoning systems with bypass dampers rather than manually shutting registers.
Myth: It costs more to turn the AC back on than to leave it running
This is perhaps the most persistent myth in home cooling: the idea that your AC has to work “extra hard” to cool a hot house down, erasing any savings you gained by turning it up while you were away.
The Truth: Heat moves to cold. The greater the temperature difference between the inside and outside of your home, the faster heat enters. By keeping your home cool all day while it is 90 degrees outside, your AC is constantly fighting a rapid influx of heat. By letting the house warm up, you slow down that heat transfer. There are proven ways to cut your cooling costs, and adjusting your thermostat by 7 to 10 degrees for eight hours a day can save up to 10% a year.
The Fix: Use a programmable or smart thermostat. Let the temperature rise while you are at work, and program it to start cooling 30 minutes before you arrive home.
Myth: A bigger air conditioner performs better
If a 3-ton unit is good, a 4-ton unit must be better, right? It will cool the house faster and handle the wildest heat waves with ease.
The Truth: An oversized air conditioner is a disaster for comfort and efficiency. Because it is too powerful, it cools the air rapidly and shuts off before it has completed a full cycle. This “short cycling” prevents the unit from removing humidity. You end up with a house that feels cold but clammy and damp. The frequent on-off cycling also puts massive stress on the compressor and fan.
The Fix: Use a Manual J load calculator rather than assuming bigger is better. A properly sized unit runs longer cycles, which keeps humidity low and temperatures consistent.
