What Size Air Conditioner Do I Need?

Whether you’re building a new home or updating your existing HVAC system, there is one question you’re definitely going to consider: what size air conditioner do I need? Selecting the ideal air conditioner size is a balancing act. Too large, and you could experience poor humidity control and exorbitant energy bills. Too small, and the unit might struggle to provide comfortable temperatures on extremely hot days. Correct air conditioner sizing is essential to enjoy an efficient, cost-effective and comfortable cooling experience.

The Importance of Sizing Your Air Conditioner Correctly

Ensuring your AC produces the right cooling capacity is a matter of comfort and cost savings. Here’s why you shouldn’t simply guess the correct air conditioning system size:

    • Humidity control: An oversized unit cools too quickly, reducing humidity removal and leaving your home clammy. A properly sized air conditioner will control indoor humidity levels more efficiently.
    • Even temperatures: A well-suited air conditioner circulates cool air evenly and decreases unpleasant temperature fluctuations between cycles.
    • Peak day performance: An undersized system will struggle to reach the target temperature on hot summer afternoons, so you need a unit powerful enough to keep up with cooling demand.
    • Proper cycling: Air conditioners start up and turn back off with sufficient run time for each cycle. Units that are larger than you need cycle too quickly, leading to unnecessary wear and tear. On the other hand, an undersized system runs continually, which may cause it to get too hot.
    • Manageable utility bills: Cycling problems caused by selecting the wrong size of air conditioner lead to higher electricity bills. However, a unit that is the correct size will work efficiently and keep your utility bills in check.

Understanding Air Conditioner Size

Cooling capacity is measured in British thermal units (BTUs). A BTU is a standard unit of energy that shows the amount of heat an air conditioner can remove per hour. The majority of room AC units range from 5,000 to 18,000 BTUs. Because central air conditioners are larger, they’re usually measured in tons. A one-ton system is equivalent to 12,000 BTUs. Generally, central AC systems range from 1 to 5 tons.

Sizing a Room Air Conditioner

When considering window or portable air conditioners, which size you need primarily depends on the room’s square footage. Measure the space—length x width—and match it to the appropriate BTUs:

    • A room measuring 150 to 350 square feet might need a 5,000 to 8,000 BTU air conditioner.
    • A room measuring between 350 and 550 square feet could need an 8,000 to 12,000 BTU unit.
    • A big room or open area of 550 to 1,000 square feet may necessitate a 12,000 to 18,000 BTU unit.

These general tips don’t take into account factors like interior heat gain or how much sun streams in through the windows of the room. For a more precise calculation, reach out to an HVAC professional from Service Experts Heating, Air Conditioning & Plumbing.

Sizing a Central Air Conditioner

Determining the perfect size of central air conditioner begins with the home’s square footage, but specific sizing requires a more in-depth look. HVAC Experts rely on load calculations outlined in Manual J to determine a home’s specific cooling requirements. Here are the considerations that come into play:

    • Square footage: How big your home is greatly affects its AC requirements, with more sizeable homes generally requiring more cooling capacity.
    • Local climate: Where you live affects your cooling needs as well. Areas with extremely hot, humid summers normally demand a higher cooling capacity than cooler, drier regions.
    • Interior heat gain: The heat released inside your home can come from people, lights, electronics and appliances. More internal heat raises your home’s cooling needs.
    • Insulation levels: The amount of insulation in your walls, attic and floors affects how much heat gets into your home. Well-insulated homes hold cool air more effectively, which lowers the cooling load.
    • Air infiltration rate: This relates to how much outside air penetrates through leaks or cracks in your home. Homes with a high air infiltration requires more cooling to counter the warm, humid outdoor air that seeps into the home.
    • Home orientation and window layout: The direction your home faces affects its sun exposure, which in turn can change the required cooling load. A single-family residence with expansive south-facing windows absorbs more heat and requires a more sizeable air conditioner than a north-facing condo.

Other Factors to Consider When Buying an AC

Besides knowing what size air conditioner you need, consider these additional factors when installing a new air conditioner:

    • Brand: Not all ACs are created equal. It’s crucial to select a trustworthy brand for dependability and longevity.
    • Efficiency rating: The seasonal energy efficiency ratio (SEER) shows the total heat an air conditioner can take out per unit of electricity it consumes. Higher SEER ratings indicate greater efficiency, reducing your utility bills.
    • Maintenance requirements: Regular maintenance keeps your system operating effectively. Most air conditioning producers encourage yearly tune-ups to locate and repair small problems before they turn into costly repairs.

Get Expert Help Sizing Your Air Conditioner From Service Experts Heating, Air Conditioning & Plumbing

Finding the right air conditioner size can be overwhelming. The Experts at Service Experts Heating, Air Conditioning & Plumbing are here to help. We can provide you with custom cooling solutions to enhance home comfort, efficiency and energy savings.

From establishing your unique cooling specifications to helping you browse different brands and efficiency ratings, we’re with you at every step. For help selecting the perfect air conditioner for your home in the U.S., call 866-397-3787 today to schedule your appointment with Service Experts Heating, Air Conditioning & Plumbing.

Savings For You

See All Offers Here >


  • Save $50 on a Paid Service
  • Written 100% Satisfaction Guarantee
  • Plus, ask how to save an additional 15% and waive your trip charge!


  • Upgrade to Worry-Free Comfort with the Advantage Program and make NO payments for 30 days!

© 2024 Service Experts, Service Experts Heating & Air Conditioning, and the Service Experts logo and design are registered trademarks of Service Experts LLC and used under license by SE Canada Inc. All Rights Reserved. *Not applicable to the Advantage Program. See your signed Advantage Program Agreement for full details and exclusions. 100% Satisfaction Guarantee is subject to certain restrictions and limitations as set forth in the applicable Terms and Conditions.

Chat with a Service Experts Professional