AC Sizing Guide
How Do I Know If My AC Is Too Small for My Home?
The most common signs of an undersized AC are a system that runs constantly without ever reaching the temperature on your thermostat, uneven temperatures between rooms, sticky or humid indoor air, and unusually high energy bills. If this sounds like your home, the issue may not be your equipment failing — it may simply be the wrong size for the space.
Signs Your AC May Be Undersized
Runs Constantly
Your system rarely shuts off, especially on hot afternoons, but the house never quite feels cool.
Uneven Temperatures
Rooms farther from the air handler stay noticeably warmer than rooms closer to it.
High Indoor Humidity
The air feels sticky or damp even when the temperature seems acceptable.
Rising Energy Bills
Your system works overtime trying to keep up, which shows up directly on your utility bill.
Why a Load Calculation Matters
- More than square footage: Insulation, window size and orientation, ceiling height, and air leaks all affect how much cooling a home needs.
- Right-sizing prevents two problems: a unit that's too small runs constantly and struggles to cool, while one that's too big short-cycles and leaves the air humid.
- Every home is different: Two homes of the same size can need very different equipment based on construction and layout.
- Included with every estimate: We perform a load calculation as part of every installation quote, at no extra cost.
AC Sizing FAQs
How do I know if my AC is too small for my home?
Common signs your AC is undersized include the system running constantly without reaching the set temperature, uneven temperatures between rooms, high humidity indoors, and unusually high energy bills. If your AC runs nonstop on hot days but your home never feels comfortable, sizing is a likely cause.
What is a load calculation and why does it matter?
A load calculation is a detailed assessment of your home's cooling needs based on square footage, insulation levels, window size and orientation, ceiling height, and local climate. It determines the correct system size, rather than relying on rules of thumb like square footage alone, which can lead to undersized or oversized equipment.
Can an undersized AC be fixed without replacing it?
In some cases, improving insulation, sealing duct leaks, or adding window treatments can reduce the cooling load enough to help an undersized system perform better. However, if the unit is significantly undersized, replacing it with a correctly sized system is usually the most effective fix.
What happens if an AC is too big for a home?
An oversized AC cools the home quickly but shuts off before it can remove enough humidity, leading to a cold, clammy feeling. It also cycles on and off more frequently, which increases wear on components and can shorten the system's lifespan.
How can I get my home's cooling load calculated?
Southern Heating and Air performs load calculations as part of every installation estimate, so you can be confident your new system is sized correctly for your home.
Get Your Home's Cooling Needs Assessed
If your AC can't keep up no matter how hard it runs, let's find out why. We'll evaluate your system and home to determine if sizing is the issue.
- Plant City
- Brandon
- Valrico
- Dover
- Seffner
- Lakeland
