What Size Air Conditioner Do I Need?

Whether you’re building a new home or updating your existing air conditioning system, there is one question you’re guaranteed to ask: what size air conditioner do I need? Choosing the correct air conditioning size is a balancing act. Too large, and you could experience poor humidity control and exorbitant energy bills. Too small, and the unit might fail to maintain comfortable temperatures on extremely hot days. Appropriate 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 air conditioning can generate the proper cooling capacity is a matter of comfort and keeping your energy bills low. Here’s why you shouldn’t merely guess the appropriate AC size:

    • Humidity control: An oversized unit cools too quickly, preventing humidity removal and rendering your home clammy. A right- sized air conditioner will regulate indoor humidity levels more effectively.
    • Even temperatures: A properly sized air conditioner circulates cool air evenly and reduces uncomfortable temperature variations between cycles.
    • Peak day performance: Systems that don’t have enough cooling capacity struggle to achieve the target temperature on hot summer afternoons, so you need a unit powerful enough to keep up with cooling demand.
    • Proper cycling: Air conditioners power on and off with sufficient run time for each cycle. Units that are too large cycle too quickly, resulting in additional wear and tear. Conversely, an undersized system runs continuously, which may cause it to get too hot.
    • Manageable utility bills: Cycling problems caused by installing the wrong size of air conditioner cause higher electricity bills. However, a unit that is the correct size will operate effectively and keep your utility bills in check.

Understanding Air Conditioner Size

Cooling capacity is expressed in British thermal units (BTUs). A BTU is a standard unit of energy that conveys the amount of heat an air conditioner can remove per hour. Most room air conditioners 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 proportionate to 12,000 BTUs. Generally, central AC units range from 1 to 5 tons.

Sizing a Room Air Conditioner

When examining window or portable air conditioners, sizing primarily depends on the room’s square footage. Measure the area—length x width—and match it to the appropriate BTUs:

    • A room measuring 150 to 350 square feet will probably need a 5,000 to 8,000 BTU air conditioner.
    • A room 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 require a 12,000 to 18,000 BTU unit.

These general guidelines don’t take into account factors like interior heat gain or sun exposure. For a more accurate calculation, contact a cooling specialist at 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 accurate sizing requires a more in-depth look. HVAC Experts rely on load calculations explained in Manual J to determine a home’s unique cooling requirements. Here are the factors that come into play:

    • Square footage: How large of a home you have significantly affects its air conditioning requirements, with bigger homes generally requiring more cooling capacity.
    • Local climate: Where you live impacts your cooling preferences as well. States with very hot, humid summers generally demand a higher cooling capacity than cooler, drier areas.
    • Interior heat gain: The heat created inside your home can be generated by people, lights, electronics and appliances. More internal heat elevates your home’s cooling demands.
    • Insulation levels: The amount of insulation in your walls, attic and floors influences how much heat gets into your living space. Well-insulated homes keep cool air more effectively, reducing the cooling load.
    • Air infiltration rate: This refers to how much outside air enters through leaks or cracks in the building envelope. Homes with a significant air infiltration requires more cooling to counteract the warm, humid outdoor air that sneaks into the home.
    • Home orientation and window layout: The direction your home faces affects its sun exposure, which in turn has an effect on your home’s cooling load. A single-family dwelling with sprawling south-facing windows absorbs more heat and calls for 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 air conditioners are created equal. It’s crucial to buy a trustworthy brand for reliability and longevity.
    • Efficiency rating: The seasonal energy efficiency ratio (SEER) shows how much heat an air conditioner can remove per unit of electricity it consumes. Higher SEER ratings signify higher efficiency, reducing your utility bills.
    • Maintenance requirements: Regular maintenance keeps your system operating effectively. Most AC makers recommend yearly tune-ups to catch small problems before they turn into expensive repairs.

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

Choosing a suitable air conditioner size can be overwhelming. The Experts at Service Experts Heating, Air Conditioning & Plumbing are here to help. We provide custom cooling remedies to enhance home comfort, efficiency and energy savings.

From estimating your unique cooling needs to helping you understand 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