--- title: "10 Mistakes You’re Making With Your Air Conditioner That Are Spiking Your Energy Bills" description: "Running your air conditioner the wrong way can lead to sky-high energy bills this summer. Make these quick fixes to trim costs now." date: "2026-07-10" modified: "2026-07-10" authors: - name: "Donna Boyle Schwartz" job_title: "Contributing Writer" link: "https://www.bobvila.com/authors/donna-boyle-schwartz/" - name: "Daryna Tobey" job_title: "Deputy Editor" link: "https://www.bobvila.com/authors/daryna-tobey/" url: "https://www.bobvila.com/interior/air-conditioner-mistakes/" categories: - "Cooling" - "Heating & Cooling" - "Interior" tags: - "ac & cooling" - "News" --- # 10 Mistakes You’re Making With Your Air Conditioner That Are Spiking Your Energy Bills ![Man adjusting the temperature on a thermostat holding $20s and $50s in his fist]() *Photo: John Brueske via Adobe Stock* These days, more than 90 percent of homes and virtually all businesses in America use air conditioning to beat the summertime heat. In fact, according to the U.S. Department of Energy, air conditioners use about 6 percent of all the electricity produced in the country. Given the overwhelming prevalence of AC, most people think they know how to maintain their system properly, whether it’s central air, a window unit, or ductless mini-splits. Many homeowners fall victim to common mistakes that waste energy, shorten the working lifespan of their air conditioner, and cost money. ## 1. Buying the Wrong Size System ![Close up of a modern AC compressor unit outdoors.]() *Photo: GalinaSt via Adobe Stock* Always use an [air conditioner that’s the right size for your home](). An oversized unit may cycle on and off too quickly, making it ineffective at removing humidity and maintaining uniform temperatures. On the other hand, a too-small unit will need to run constantly, which will drastically shorten its lifespan. Determine your needed cooling capacity by doing a load calculation, taking into account each room’s square footage, layout, insulation, function, and typical occupancy. ## 2. Cooling an Empty House ![Home interior with hardwood floors and open floorplan showing dining room, kitchen, and living room. Has high vaulted ceilings.]() *Photo: Justin Krug via Adobe Stock* Because cooling an empty house wastes both money and energy, it's a good idea to upgrade to a [programmable home thermostat](). This technology allows you to raise and lower the temperature of your air conditioner based on a preset schedule, which can save hundreds of dollars annually. Boost your energy efficiency even more by keeping closet and cabinet doors shut so excess air doesn’t get in. ## 3. Poor Position of the Thermostat and Vents ![A plant in a seagrass planter is positioned in front of a low air conditioner vent on a wall.]() *Photo: NC Photo via Adobe Stock* Inside your home, make sure the thermostat is properly positioned and vents allow for proper air circulation. Place the thermostat away from direct sunlight and heat-producing lights and [appliances]() so you do not get inaccurate readings, and cause the air conditioner to work overtime. Do what you can to make sure that AC vents are not blocked by plants, furniture, or curtains. ## 4. Not Using Fans to Circulate Cool Air ![Luxury living room with brick wall and antique stove. View of leather love seats. Room decorated with fake tree in a wicker pot]() *Photo: Iriana Shiyan via Adobe Stock* If possible, combine your air conditioning with the use of strategically placed fans. Any type of fan helps cool the air circulating throughout your home, which will make you feel more comfortable at a higher indoor temperature. Be sure to [set ceiling fans to run counterclockwise]() during the summer in order to push the air downward. Note that you should also minimize the use of [exhaust fans in the bathroom]() and kitchen while you're running the AC, as these remove cool air from your home. ## 5. Leaving Your Windows Open When the AC is on ![Hand pulls lever to open a white PVC window, with a green plant nearby indoors.]() *Photo: nadyarakoca via Adobe Stock* [Open windows]() and doors and windows invite humidity inside your home and let chilled air escape. Your air conditioner must then work extra hard to compensate, wasting vast amounts of energy along the way. Always keep doors and windows closed when the AC is running. ## 6. Forgetting to Clean the Filter ![Woman inserts new filter into her furnace.]() *Photo: Tom Fenenga for BobVila.com* Clean or replace [HVAC air filters]() every month during the cooling season, and more frequently if the filter seems excessively clogged with dust and debris. A [clean AC filter]() significantly improves an air conditioner’s efficiency, lowering your energy consumption by 5 to 15 percent. On central air conditioners, filters are typically located on the return ducts in walls or ceilings. Room air conditioners have a filter mounted in the front-facing grille, while ductless mini-splits house their reusable filters in a removable panel. Consult your owner’s manual for exact instructions on changing the air filter. ## 7. Allowing Debris to Pile up Around the Condenser ![Woman uses a leaf blower to clear debris around air conditioning unit outside.]() *Photo: Tom Fenenga for BobVila.com* Outdoor condenser and evaporator coils can become clogged with dirt, which blocks airflow and insulates the coils, reducing their ability to manage heat efficiently. To keep the coils from clogging, don’t place your AC components near dryer vents, and remove fallen leaves, grass clippings, and other outdoor debris regularly. Trim shrubs and other foliage to give at least 2 feet of space around the condenser, allowing for adequate airflow. Our guide to [cleaning air conditioning coils]() can help you keep your condenser in tip-top shape. ## 8. Not Attending to Routine Maintenance ![Woman pours vinegar through a funnel into the condensation drain of an AC.]() *Photo: Tom Fenenga for BobVila.com* Properly maintaining your air-conditioning equipment will maximize its operating efficiency and effective lifespan. At the beginning of the cooling season, inspect the seals on the air conditioner as well as the seals between the unit and the house to ensure no cool air is escaping. Then, check the fuses, circuit breakers, wire, and terminals for corrosion; [clean the condensate drain line](); and examine fans and other moving parts for signs of wear. ## 9. Putting the AC Unit in Direct Sunlight ![Metal air conditioning unit outside a house, on a concrete slab.]() *Photo: Scott Habermann via Adobe Stock Christopher Scott Habermann* Although air conditioners aren’t the most attractive items in a landscape, homeowners shouldn’t try to “hide” their unit in an inopportune spot. The location of an air conditioner has a big impact on its energy efficiency. Try installing it in a shady spot on the east or north side of your house, because too much direct sunlight will make the system work harder. Additionally, don’t place concealing shrubs or plants too close to the unit, as these will impede ventilation and may clog the condenser coils. ## 10. Not Calling an HVAC Professional When You Need One ![HVAC professional uses tools to check for a refrigerant leak.]() *Photo: ungvar via Adobe Stock* Some air-conditioning systems issues, such as refrigerant leaks, can only be diagnosed and repaired by a qualified HVAC technician. Have an [HVAC professional inspect and tune up your system]() on a regular schedule, ideally annually. A routine service call is going to be far cheaper than the [cost of an AC repair]() emergency. ## Author Donna Boyle Schwartz is an avid writer with years of experience covering the home and garden beat in addition to out-of-home topics such as sports and local events. These days, she researches and writes editorial and advertising features on a vast range of home-related topics, including housewares, furniture, home fashions, flooring, remodeling, construction, antiques, art, garden, collectibles, and color/design trends.