No publications conduct comparative reviews of furnaces or comprehensively rate an individual model, but it's easy to see why. A tester would have to install furnaces in identical homes to compare them. How well a furnace functions depends on the installation of the whole system, including ductwork and venting. Factors such as climate, home size, insulation, window condition and usage will also affect performance. Even evaluating the long-term reliability of a particular model is problematic because furnaces are made to last 15 to 20 years, and technology can change a lot over such a long period. Comparing the repair records of different brands is possible, but the editors of ConsumerReports.org say they "found no statistically meaningful differences in percent of models ever repaired for the leading brands of furnaces" in their research.
So, if testing specific furnace models is very difficult, how should you choose a furnace? Experts generally say that the best way is to choose a reliable contractor and let that person's expertise guide you. A skilled heating, ventilation and air conditioning (HVAC) contractor will evaluate your home's energy needs and help you choose a furnace that is the right size and efficiency for you, based on a number of factors. Sources such as ConsumerReports.org, EnergySavers.gov, the American Council for an Energy-Efficient Economy (ACEEE) and home-improvement expert Danny Lipford offer useful advice on choosing and working with a furnace contractor. One commonly cited tip is to hire a certified installer. Two associations that certify furnace and boiler installers are North American Technician Excellence (NATE) and HVAC Excellence. Sources most often recommend using a NATE-certified installer.
Although it is not possible to evaluate everything about a particular furnace, you can look for particular features that are important to you. Perhaps the most important feature of a furnace is its overall energy efficiency. The percentage of fuel a furnace converts to usable heat is its annual fuel-utilization efficiency, or AFUE. All new furnaces made and sold in the United States must have an AFUE of at least 78 percent, and nearly all furnaces perform at 80 percent AFUE or better. However, high-efficiency furnaces can achieve an AFUE as high as 97 percent, meaning that only 3 percent of the heat extracted from fuel is lost through exhaust. Sources such as the ACEEE and EnergySavers.gov can help you estimate how much money you could potentially save on your annual heating bills by installing a more efficient furnace.
Replacing an ailing or old furnace can also get you a tax credit. Additional tax credits and other rebates may be available from your state government or from your utility company.
With few exceptions, furnaces and installation are sold as package deals. Buying your furnace directly from the manufacturer offers potential savings, because many HVAC contractors include a substantial markup in the prices of the furnaces they sell. However, this approach poses problems, as well. The first problem is figuring out what size furnace you need, which involves a complicated formula known as a load calculation. You will either need to hire a contractor to perform the load calculation or buy software to help you do it yourself. A second problem is that some HVAC manufacturers will void the warranty on any furnace that is purchased outside of the contractor relationship. However, most manufacturers will honor the warranty as long as the furnace is bought through a licensed distributor and installed by a licensed HVAC contractor. This leads to the third problem: finding a contractor willing to install the equipment you have purchased, as some contractors are not willing to install furnaces that they haven't sold themselves.