Do you have the necessary ductwork? If you're replacing an existing central air conditioner, then your house will already have a system of ducts in place. However, your contractor should still check out the ducts to make sure they are in good condition. Be sure to tell the contractor about any problems you are having with airflow or uneven cooling with your existing system, since this may be a sign of poorly designed ductwork. If you are adding a new air conditioner, you may be able to connect it to the ductwork for your central heating system, although it may need some modifications. If your home has no ductwork, you might want to consider a ductless mini-split system.
Consider your climate. If you live in a hot, humid climate, it's especially important to choose an air conditioner with a high SEER, since the air conditioner will be running a lot. In a hot, dry climate, EER is more important than SEER; it measures how effective the air conditioner will be in the hottest weather. In mild climates, consider a heat pump, which could meet your needs for heating as well as cooling. We discuss heat pumps in our separate report on furnaces.
Get at least three quotes from contractors. Regardless of the central air conditioner system you select, the difference between a great choice and a poor one often comes down to the contractor you select. Referrals from friends, neighbors and co-workers can be a good starting point. You can also ask local trade organizations for names of members in your area. Organizations like the Air Conditioning Contractors of America (ACCA) have directories on their websites that can be searched by ZIP code.
Get all the details. Don't trust a contractor who gives you an estimate based solely on your home's square footage. Make sure the contractor calculates your home's cooling needs according to Manual J, a tool published by the ACCA, and get a written estimate that shows all calculations, including ductwork design.
Check out the contractor's credentials. Ask to see the contractor's license and proof of insurance, and find out how long the company has been in business. ConsumerReports.org recommends looking for a company whose technicians are certified by a trade organization, such as North American Technician Excellence (NATE) or HVAC Excellence. Get at least three references from each contractor, and be sure to check them. A check with your local Better Business Bureau is a good idea as well.
Compare bids. Don't rely solely on price; you should expect to pay more for quality work. An extremely low bid is a warning sign that a contractor is likely to cut corners. The ACCA provides a handy guide on their website to compare bids based on both price and quality.
Negotiate for the best deal. An estimate isn't set in stone. If you have another bid that's lower, ask the contractor to explain the discrepancy. If you ask for a relatively small discount, you will probably get it. You can also negotiate for a better warranty or service contract.
Get it in writing. Make sure to get a written contract before the work begins. Project costs, scheduling, model numbers and warranty information should all be specified. This will protect you from unwanted last-minute changes.
Rebates come and go, and can vary by locality and power company, but when available, can help defray the cost of a new central air system. Check with your local authorities and energy companies to see what's currently available. A database of energy incentives and polices is also available here.