Air Conditioner Installation Costs. As you can see above, the average cost to install all air conditioning units is roughly $4,700. Nonetheless, your AC unit cost will largely depend on the size you need. If your home is 1,600 square feet, a 2.5 ton air conditioner will cool it well and cost between $3,000 and $5,000. There are platinum models that could potentially cost $10,000, but these are rarely necessary.