By Sean Gallagher, Regional Sales Manager Mitsubishi Electric

If your air conditioning bill seems unusually high this summer, you're not alone. Higher outdoor temperatures, rising electricity rates, and increased cooling demand can all contribute to higher energy costs.

In most homes, a high AC bill is caused by one or more of the following factors:

  • An aging or inefficient HVAC system
  • Lack of routine maintenance
  • Oversized systems short cycling
  • Cooling rooms that aren't being used
  • Equipment that runs longer than necessary

The good news is that many of these issues can be addressed through simple changes, regular maintenance, or more efficient HVAC technology that is properly sized and applied for the home’s layout, comfort needs and cooling demands.

Why is my air conditioner running all the time? During periods of extreme heat, it's normal for an air conditioner to run longer than usual. However, if your system seems to run constantly or struggles to maintain the temperature you've selected, it may be working harder than necessary.

Older systems, dirty filters and deferred maintenance can all reduce efficiency and increase cooling costs. Airflow problems can also reduce your system’s efficiency by up to 15%, according to ENERGY STAR®. Without periodic service, smaller issues such as refrigerant leaks, dirty outdoor compressor coils, worn parts, or tears and gaps in ductwork can go unnoticed, allowing cooled air to escape before it reaches the rooms that need it.

What you can do:

  • Schedule seasonal HVAC maintenance Your HVAC system is a machine that needs regular maintenance to keep working in top shape, much like your car.

  • Ask your contractor to check for holes, cracks or leaks in your ductwork Ductwork can develop holes, cracks or loose connections over time, especially in attics or crawl spaces. When that happens, cooled air can leak out before it reaches the rooms that need it, making the system run longer and work harder to keep the home comfortable.

  • Replace or clean air filters regularly This is an easy task many homeowners can do on their own. A clean filter helps keep the system cleaner and can also help reduce allergens in the home, which may make spring and fall easier to manage for people with seasonal allergies.

  • Keep outdoor units free of debris Because outdoor units are often installed at ground level, dirt, roots, leaves and small animals can collect around the equipment over time. Keeping the area clear throughout the year can support system longevity and efficiency. Depending on the size and application, some outdoor units may also be wall mounted, which can make routine upkeep easier.

  • Set a comfortable temperature and keep it there Choosing a steady temperature can help reduce unnecessary adjustments that make the system work harder. Instead of constantly turning the thermostat up or down, pick a setting that feels comfortable and let the system maintain it consistently.

Can a poor home envelope make my AC bill higher? Yes. Your home’s envelope includes the walls, attic, floors, windows, doors and other areas that separate conditioned indoor air from outdoor heat. If the home is under-insulated or has air leaks, cooled air can escape while hot, humid outdoor air gets in, forcing the HVAC system to run longer to maintain comfort.

Weatherization is key to creating an energy-efficient building envelope. A tighter, better-insulated home can reduce the cooling load, and the smaller the load, the smaller the equipment needed tends to be. That can support both upfront and long-term savings for homeowners while helping the system cool the home more efficiently.

Signs your home envelope may be part of the problem:

  • Rooms that feel hot, humid or drafty
  • Uneven temperatures from room to room
  • Attics, crawl spaces or duct areas that are poorly insulated or unsealed
  • An AC system that runs often but still struggles to keep up

What you can do:

  • Ask a qualified professional to evaluate insulation levels, air sealing and duct sealing
  • Seal gaps around areas where air can leak, such as attics, crawl spaces, windows and doors
  • Consider weatherization improvements before replacing equipment so the system can be sized for the home’s actual cooling load

Can cooling unused rooms increase my energy bill? Yes. Many homeowners cool their entire home even though they spend most of their time in only a few rooms. Conditioning unused spaces requires additional energy and can increase monthly cooling costs.

Think of it like plumbing. If your plumbing worked the way many HVAC systems do, turning on one shower would also turn on every other shower and sink in the house. That would waste water in places you are not using. Cooling can work the same way. Many homeowners cool the entire home even though they spend most of their time in only a few rooms. Focusing comfort on the spaces you actually use, when you use them, can help reduce unnecessary energy use while keeping the home comfortable.

What you can do:

  • Adjust your thermostat only when you’ll be away for an extended period, such as during a vacation On a typical day, keeping the thermostat at a steady, comfortable temperature can help the system operate more efficiently. Frequent adjustments may cause the system to work harder as it tries to bring the home back to the preferred setting.

  • Close blinds and curtains in rooms you are not using Windows can let heat into the home quickly, especially during the hottest parts of the day. Closing blinds or curtains in unused rooms can help reduce heat gain and make it easier for the system to maintain comfort.

  • Use zoning capabilities if your system supports them Zoning allows you to control temperatures in different areas of the home. That means less arguing with your family over the thermostat and more personalized comfort, so everyone can enjoy the temperature they want in their favorite room.

  • Focus cooling on the areas where your family spends the most time Prioritizing frequently used rooms can help reduce unnecessary cooling in empty spaces and keep comfort focused where it matters most.

When should I replace an older air conditioner? If your system is more than a decade old, requires frequent repairs, or struggles to maintain comfort, it may be time to evaluate replacement options.

A decade ago, minimum efficiency requirements for many systems were around 12 to 13 SEER, while some of today’s advanced systems can reach nearly 36 SEER2. That difference can make replacement worth considering, especially if an older system is using more energy or no longer keeping the home consistently comfortable.

What you can do Ask an HVAC professional to evaluate:

  • System age Depending on the system’s age, a contractor can help determine whether repairs, warranty coverage or replacement should be considered.

  • Repair history Reviewing repair history can help identify recurring issues and determine whether routine service could improve comfort before investing in a new system.

  • Energy efficiency An efficiency check can reveal whether the system is using more energy than it should and help uncover potential issues before they become larger problems.

  • Proper sizing of the existing system, ductwork and related components Proper sizing is important because an oversized or undersized system can affect comfort, efficiency and long-term performance. A contractor can also evaluate ductwork and related components to make sure the full system is designed to support the home’s actual cooling needs.

A replacement may reduce operating costs while improving comfort throughout the home. Check with your trusted HVAC advisor about possible rebates and incentives for upgrading your HVAC system.

What HVAC technology can help lower cooling costs? While maintenance and everyday habits can help reduce energy use, newer HVAC technologies are designed to improve efficiency over the long term.

  • All-Electric Heat Pumps Modern heat pumps are designed to provide highly efficient heating and cooling and may use less energy than older HVAC systems. Newer models can adjust their output to match changing comfort needs, helping maintain more consistent temperatures throughout the home. However, actual energy use depends on factors such as home insulation, ducts, zoning, and proper system sizing and installation.

  • Inverter-Driven Technology Unlike conventional systems that repeatedly turn on and off, inverter-driven systems adjust output based on demand, reducing those hard energy spikes and inefficient ramp up periods. This helps maintain more consistent temperatures while reducing energy waste.

  • Zoned Comfort Zoned systems allow homeowners to target their cooling needs in specific areas of the home independently, helping to reduce energy use in unoccupied spaces. There are now many ways to zone HVAC equipment, including options that do not require ductwork.

Small Changes Can Make a Big Difference A high AC bill is often caused by a combination of equipment performance, maintenance needs, cooling habits, and home energy use.

Simple changes such as adjusting thermostat settings and scheduling regular maintenance can help improve efficiency and lower cooling costs. For homeowners looking for long-term savings, modern HVAC technologies offer additional opportunities to improve comfort while using energy more efficiently.

Sean Gallagher, Regional Sales Manager Mitsubishi Electric LinkedIn

Sean Gallagher is a Regional Sales Manager for Mitsubishi Electric Trane HVAC LLC serving Western Massachusetts and Vernmont markets with specialties in Sales, HVAC Product Application and Contractor Development. Sean has served the HVAC Industry for the last 25 plus years in roles ranging from HVAC Sales, Technical Training and HVAC Education. He is passionate about the HVAC field and heavily involved in providing training and customer service to HVAC contractors with focus on the Northeast region.