How to Make Air Conditioner More Efficient? | 7 Habits That Cut AC Costs

Your air conditioner works hardest when it fights the sun, your own appliances, and a dirty filter. The good news: most efficiency gains come from habits, not hardware. Sealing leaks, clearing vents, and shading the outdoor unit can trim cooling costs without sacrificing comfort. Here’s exactly where to start, in order of impact.

Set the Thermostat to 78°F and Let Fans Help

ENERGY STAR and utility guidance consistently recommend 78°F as the target cooling setpoint for efficiency. Raising the thermostat when you’re away or asleep is even better—utility guidance says raising it 10 to 15 degrees when out may save 5 to 15% on energy bills.

A programmable or smart thermostat automates those setbacks so you don’t have to remember. If you want to push the setpoint higher, run a ceiling fan in occupied rooms. Fans can make a room feel about 4°F cooler, which means you can raise the thermostat a few degrees without noticing the difference. Just turn the fan off when you leave the room—fans cool people, not rooms.

Change Air Filters Monthly in Heavy-Use Months

A dirty filter chokes airflow, forcing the system to run longer and work harder. Check the filter every month during summer and winter heavy-use periods, and replace it if it’s dirty. At minimum, swap it out every three months.

This is the single easiest efficiency win available to any homeowner. A clean filter costs a few dollars and takes two minutes to change. If you use a reusable filter, clean it according to the manufacturer’s instructions instead of replacing it.

Seal Ducts and Clear Airflow Obstructions

Leaky ducts waste a significant share of cooled air before it reaches your living spaces. ENERGY STAR’s duct-sealing sequence starts with ducts in the attic, crawlspace, unheated basement, or garage—those are the worst offenders. Seal seams and connections using duct sealant (mastic) or metal-backed (foil) tape. Skip ordinary cloth duct tape; it degrades quickly and fails as a permanent seal. After sealing, wrap those ducts in insulation.

Airflow matters just as much as sealing. Keep supply and return vents free of furniture, rugs, and curtains. Clear weeds and debris away from the outdoor condenser unit so its coils can breathe. If the outdoor unit sits in direct sun and shade is available, some shade helps it run cooler—just don’t restrict airflow around the unit itself.

Run Hot Appliances at Night and Consider an Upgrade

Ovens and dryers generate serious heat. Running them during the hottest part of the day forces your AC to counteract both the outdoor heat and your indoor heat sources. Shift laundry and cooking to cooler evening hours where possible, and close the door to rooms you aren’t cooling.

While central air benefits most from duct sealing, room and window units respond best to clean coils, filter changes, and shade. If your system is old or repairs keep stacking up, an ENERGY STAR–rated unit can cut cooling costs substantially. Our tested roundup of top-rated energy efficient air conditioners breaks down which models actually pay off.

Common Efficiency Mistakes to Avoid

• Using cloth duct tape on duct seams—always use mastic or foil tape instead.
• Skipping filter changes—a dirty filter forces longer run times.
• Blocking vents with furniture, rugs, or decor restricts airflow.
• Leaving the outdoor unit in direct sun when shade is readily available.
• Cooling unoccupied rooms instead of using thermostat setbacks or zoning.

FAQs

What temperature should I set my AC to in summer?

Set it to 78°F when cooling is in use, per ENERGY STAR and utility guidance. When you’re away or asleep, raise the setpoint by 10 to 15 degrees to save an estimated 5 to 15% on energy costs. A programmable thermostat makes these setbacks automatic.

How often should I replace my AC filter?

Inspect the filter monthly during heavy-use summer and winter months. Replace it if it looks dirty, and change it at least every three months regardless. Reusable filters should be cleaned per the manufacturer’s instructions instead of discarded.

Does duct sealing really improve AC efficiency?

Yes, especially for ducts running through unconditioned spaces like attics and crawlspaces. Use mastic or foil tape on seams and connections, then wrap ducts in insulation. ENERGY STAR recommends sealing unconditioned-space ducts first, then tackling accessible ducts in conditioned areas.