As an energy expert, I get a lot of questions this time of year about staying cool without driving up energy costs. But one question lands in my inbox more than almost any other:

"Should I keep my A/C set to ON or AUTO?"

It's a great question because that small setting on your thermostat can have a bigger impact than most people realize.

AUTO vs. ON: What's the difference?

For most homes, AUTO is the better choice.

When your thermostat is set to AUTO, the fan runs only when your air conditioner is actively cooling your home. Once the desired temperature is reached, the fan shuts off.

When it's set to ON, the fan runs continuously, even when your A/C isn't cooling.

While some people think keeping the fan running all the time helps maintain a more even temperature throughout the house, it also uses more energy and can increase wear on the fan motor.

In fact, if your air conditioner normally cycles off about 30% of the time, switching from AUTO to ON can add more than 200 extra hours of fan run time each month.

What's the best temperature to stay cool and save?

Once we settle the ON versus AUTO debate, customers usually ask another question:

"What temperature should I set my thermostat to?"

A good rule of thumb is to set your thermostat to a comfortable temperature between 75°F and 78°F when you're home and around 82°F when you're away.

Here's a quick tip: Each degree you raise your thermostat above 75°F can save up to 5% on your monthly cooling costs, depending on your home and A/C system.

A few more ways to help your A/C work smarter

Small changes can add up when temperatures soar.

• Keep vents open. Closing vents can make your system work harder and use more energy.
• Stay on top of maintenance. Clean filters and regular tune-ups help your system perform more efficiently.
• Consider a smart thermostat. It can automatically adjust temperatures based on your schedule and help avoid unnecessary cooling.
• Use fans wisely. Ceiling and box fans cool people, not rooms. Turn them off when you leave to avoid wasting energy.

Don't wait until your system quits

Many customers ask about rebates after they've already purchased a new A/C system. If your unit is more than 10 years old, it's worth exploring your options before you need an emergency replacement.

Start your install with a Participating Independent Contractor and receive an instant $150 rebate.