Tips for Buying a Furnace

Learn how to compare funaces and purchase the right one

By Sylvia Cochran

Photo by iStockphoto.com

Buying the right furnace can save you money in energy costs, increase the eco-friendly nature of your home and -- in addition to efficiently heating your home -- net you a tax credit. A furnace is the primary home heating appliance. Secondary heating sources -- such as a wood stove or fireplace -- fulfill occasional or ornamental purposes but do not generally heat a whole house.

Types

Choose between a condensing, sealed-combustion, or variable-speed furnace. The condensing models hold the seal of approval from the American Council for an Energy-Efficient Economy; they are more expensive than other types but reduce your energy costs in the long run. Sealed-combustion models are impervious to vapor damage. Variable-speed units are quieter and allow for an energy-saving reduction of fan speed.

Fuel Options

Decide on the fuel that is most available and cost effective in your area. Oil, propane and gas now power home furnaces. Fuel oil easily clogs nozzles, so oil furnaces must be cleaned and serviced more often than their counterparts. Oil-powered furnaces also do not offer the efficiency of their gas-powered cousins. Due to the rise of heating oil prices, gas is now the most commonly used heating fuel.

Sizing

Your furnace's size must match your home's heating requirements. A furnace that is too large for your home turns on more often than is necessary, may overheat the area and -- since it needs larger than average ducts -- may operate noisily, unless you upgrade the duct size at the same time as the furnace. Hire a reputable HVAC contractor to perform a load calculation of your home, which incorporates the overall size of living space, the presence or absence of insulation and the design of the house.

Efficiency

Notice that a gas furnace provides you with an "annual fuel utilization efficiency rating" -- also known as AFUE -- that lets you know how much heat the furnace generates from a therm of gas. Look for a high number, since this indicates high efficiency, which translates into lower heating costs. The minimum AFUE rating for a new non-condensing fossil-fueled, warm-air gas furnace is 78 percent, but there are quite a few models that exceed this requirement by around 20 percentage points.

Cost

It may seem like the best idea to purchase a high AFUE gas furnace. Before you make this rather sizable investment, think through the cost of the appliance and the potential for realizing all of the energy savings. For example, a 90 percent AFUE rating can increase the cost of the furnace by $1,000 when compared to an 80 percent model. The savings you'll realize on a 90 percent model furnace over an 80 percent model is only about $11 for every $100 dollars you spend on heating. If you spend $1,000 dollars annually on heating, your projected savings will be approximately $110 per year. Unless you remain in your residence for at least nine years, you will not realize a net benefit from the energy savings associated with the higher priced 90 percent AFUE model over the lower cost 80 percent model.