Getting Started

Unless you happen to know a heating, ventilation and air conditioning guru, finding an HVAC pro can be a shot in the dark. Start by searching for someone who's rated and reviewed well in your area: Find a local HVAC contractor.

After you've found a few local contenders, cross-check their credentials through the Air Conditioning Contractors of America (ACCA) or the Sheet Metal and Air Conditioning Contractors' National Association (SMACNA). Most residential HVAC professionals belong to one or both.

Plan to interview several contractors so you can compare. The following questions can help you suss out the wheat from the chaff.
Are you NATE certified?
In most states, a license is required to be an HVAC contractor. First, ask for the license number and look it up with the National Contractor License Service.

Focus on contractors who are certified by North American Technician Excellence (NATE). Many NATE members are also affiliated with ENERGY STAR, which approves energy efficient appliances.
Are you insured?
Chances are, nothing will happen other than a smooth installation. But since HVAC technicians will be in your home monkeying with heavy equipment, make sure the company carries both worker's compensation and liability insurance to cover any damage done to your home or the contractor.
How will you determine what size HVAC I need?
One of the biggest mistakes people make with HVACs is getting one that's too large, which wastes energy and money. To determine the right size for your home, reputable companies and contractors use the "Manual J" load analysis when installing a new system. Manual J is a calculation that takes into account your home's age, number and condition of its windows, insulation, number of floors, square footage, local energy rates and other factors.

Beware the contractor who merely bases the size of the new HVAC on the size of your existing one. Often these systems are out of date or were not properly sized from the start. A good contractor should also ask you about any heating or cooling issues you've been having to ensure they're addressing all possible solutions.
Are there more energy efficient options?
Quality contractors should be up on the latest energy-saving equipment options, including ENERGY STAR. Sometimes these options have a higher initial cost, but will save you in the long run. Go with a contractor who will discuss all options and is not focused solely on price.
What about warranty?
Check to see if your current system is still under warranty. Some costs may still be covered. Reputable contractors will abide by the terms through the warranty period. If you're past warranty and getting a new system, get any guarantees for the new equipment in writing.
Is there any regular maintenance I should be doing?
Before your technician leaves, make sure they show you any regular maintenance required, such as changing filters or operating the thermostat. Many heating/cooling companies recommend you replace or clean filters once a month depending on their type. Have your system checked and serviced twice a year to ensure maximum efficiency and get ahead of any potential malfunctions, especially prior to major temperature changes in summer and/or winter.
Will someone inspect the system?
It's standard practice for a technician to come and check the system to make sure it's working properly, usually around 30 days after installation. Confirm this in advance.
Can I get a bid and references?
Any HVAC contractor worth their salt will provide you with a written bid or estimate detailing the work to be done, equipment installations and price, including labor. Check references, and to be safe, get proposals from three different contractors before making a final call.

Resources: U.S. Department of Energy, Air Conditioning Contractors of America (ACCA), American Council for an Energy-Efficient Economy (ACEEE)