HomeAdvisor’s Air Conditioning Cost Guide lists price information on installing a new A C unit, as reported by HomeAdvisor customers..NOTE If you have multiple AC unit on your home, you can use the same square footage estimator based on how much area each unit covers. Your install contractor will verify during the job site inspection that you have ordered the correct tonnage, andist with any necessary correction to your order prior to installation..I am considering replacing a ton AC unit with a . ton unit. The reasoning is that the unit’s job is to cool an area just over , square feet, and I must replace the unit either way..For a good, not necessarily top of the line,nd. Cost of compressor plus installation. For a bedroom average size ranch and ba.t. I live in.