Is a 3-ton AC unit good for 1200 sq ft?

Is a 3-ton AC unit good for 1200 sq ft is generally oversized for most homes and likely too big, causing short cycling, poor humidity control, and higher bills, unless you have extreme conditions like very poor insulation, high ceilings, or very hot desert climate. Standard rule of thumb is 1 ton per 500 to 600 sq ft for average insulation, so 1200 sq ft would typically need 2 to 2.5 tons, not 3 tons. 3-ton equals 36,000 BTU per hour, which is about 50 percent more capacity than needed for well-insulated 1200 sq ft home that would need 2 tons or 24,000 BTU. Oversized 3-ton unit will cool air quickly in 5 to 10 minutes and shut off, but will not run long enough to remove humidity from air, leaving home feeling cool but clammy and humid at 60 to 70 percent humidity, which encourages mold and dust mites. It also causes more frequent on-off cycles that increase wear on compressor and raise electric bills. Exceptions where 3-ton for 1200 sq ft may be appropriate include older home built before 1970 with poor insulation and single pane windows, home with 12 foot ceilings and large open great room, or location in Phoenix where outdoor temperature exceeds 110 degrees and Manual J shows high load. Proper sizing requires Manual J calculation that considers insulation, windows, air leakage, not just sq ft. For 1200 sq ft, 2 to 2.5 ton variable speed is usually ideal.