A 1800-square-foot home typically needs a 5,000-6,000 BTU air conditioner per 500 square feet, totaling 18,000-22,000 BTUs. This equals a 1.5-2-ton central AC unit.
Air conditioner sizing depends on cooling capacity, measured in British Thermal Units (BTUs). One ton of cooling equals 12,000 BTUs. For accurate sizing, calculate the total square footage and adjust for climate, insulation, and sun exposure.
| Type | Size Range | Best For |
|---|---|---|
| Window units | 5,000-30,000 BTUs | Single rooms |
| Mini-splits | 9,000-48,000 BTUs | Zoned cooling |
| Central AC | 18,000-60,000 BTUs | Whole homes |
An undersized unit won't cool effectively, while an oversized unit wastes energy and money. The U.S. Department of Energy recommends sizing air conditioners correctly to maximize efficiency.
Many assume bigger is better, but oversized units cycle on and off too frequently, reducing efficiency and increasing wear. Proper sizing balances comfort and cost.
For example, a 1800-square-foot home in a hot climate may need a 2.5-ton unit, while the same home in a milder climate could manage with a 2-ton unit. Always factor in insulation quality and window count.
To determine the right size, follow these steps:
I once helped a friend choose an air conditioner for their 1800-square-foot home. After calculating the BTUs needed and considering their poorly insulated attic, we opted for a 2.5-ton unit. It kept the house comfortable even during peak summer heat.