A 2.5-ton air conditioner is best because approximately 30,000 BTUs are needed for a 1500 square foot home. As a general rule, 30,000 BTUs are needed for 1500 square feet. So you need a 2.5-ton air conditioner for a 1,500-square-foot room. If your room is less than 1,500 square feet but more than 1,200 square feet, you can use a 2-ton air conditioner.
I have been working as a professional in the air conditioning industry for more than 7 years, ranging from design and installation to start-up and maintenance.