Short answer: most 1,500 sq ft houses need a 2.5 to 3 ton air conditioner — that is 30,000 to 36,000 BTU. Hot southern climates land on 3 tons; mild climates and well-insulated homes can run 2.5 tons.
AC size for 1,500 sq ft by climate
| Climate | Recommended size |
|---|---|
| Hot (Florida, Texas, Arizona) | 3 tons (36,000 BTU) |
| Moderate (Carolinas, Tennessee, Oklahoma) | 2.5 tons (30,000 BTU) |
| Cool (Pacific Northwest, New England) | 2 to 2.5 tons (24,000–30,000 BTU) |
Why bigger is not better
An oversized AC cools the air fast and shuts off before pulling out humidity, so the house feels cold and clammy, and the constant start-stop cycling wears the compressor and raises bills. Undersized is just as bad — it runs all day and never catches up on the hottest afternoons. Right-sizing is the goal.
What else changes the size you need
Insulation and air sealing are the biggest factors after climate — a leaky, poorly insulated 1,500 sq ft home can need a full ton more than a tight one. Ceiling height, window area and sun exposure, and how many people live in the home all move the number too. For a final central-AC decision, ask your installer for a Manual J load calculation rather than a rule of thumb.
Sizing one room or a window unit instead? Use our BTU calculator — it adjusts for ceiling height, insulation, sun and occupants.