Tons, not square feet
Air conditioners are sized in tons of cooling capacity (one ton is 12,000 BTUs per hour). You'll hear rules like "one ton per 500 square feet," but those shortcuts ignore the things that actually drive your cooling load.
What a load calculation looks at
A proper load calculation, often called a Manual J, accounts for:
- Square footage and ceiling heights
- Insulation levels in walls and attic
- Window size, type and which direction they face
- Shade from trees (Kingwood's canopy can make a real difference)
- Air leakage and ductwork location
- The number of people and heat-producing appliances
Why oversizing is a problem in our climate
In humid areas like Lake Houston, an oversized system is worse than you'd expect. It cools the air so fast that it shuts off before it has removed much moisture. The result is a house that hits the thermostat setting but still feels damp, plus more wear from frequent starts. A right-sized or variable-speed system runs longer, gentler cycles that pull out humidity.
Why undersizing is a problem too
An undersized system runs nonstop on the hottest afternoons and may never reach the set temperature. That's why simply copying the size of the old unit isn't enough, especially if the home has had new windows, added insulation or an addition since the original install.
Don't forget the ducts
Even a perfectly sized system will underperform with leaky or undersized ducts. Ask your contractor to check them as part of any AC replacement quote. See ductwork and airflow.