Experts recommend that you replace your furnace if it is more than 15 to 20 years old. You should also consider replacing any furnace that does not have vent dampers or a draft fan, has a pilot light rather than electronic or hot-surface ignition, or it is a coal-burning model that has been converted to gas or oil. But once you decide it’s time to replace your furnace, how do you decide what one you need? Here are a few factors to consider when purchasing your new furnace.


A furnace that is too small can’t warm your home in extreme cold. To avoid that possibility, many homeowners choose furnaces that are larger than necessary. Beyond the downside of the increased initial price, a furnace that’s too large will cycle on and off more frequently (short cycling), putting more wear on its components, wasting energy, increasing utility bills, and possibly causing uncomfortable temperature variations. The climate in the region of the country you live in along with your home’s square footage, design, and construction are factors for determining the right sized furnace for your home. A reputable HVAC contractor can help you determine this.


When selecting a furnace, pay close attention to the Annual Fuel Utilization Efficiency (AFUE) number (shown as a percentage) which represents how efficiently the furnace converts gas to heating energy. A higher percentage means more energy-efficiency. The lowest efficiency allowed by law for new gas furnaces is 78%, and some new models achieve 97%, near-total efficiency. It’s also important to look for Energy Star products. Energy Star furnaces meet the Environmental Protection Agency’s (EPA) standards by using less energy (20-40%), thus reducing pollution. To help with your decision, ask your contractor to select models in a range of efficiencies and calculate the annual estimated operating cost of each model.

Variable Speed

Typical furnaces consume 400 watts of energy in continuous fan mode while some furnaces with variable-speed technology use only 60 to 80 watts. Besides providing exceptional comfort, this technology also saves homeowners money on their energy bills and can also help control high humidity.

Two-stage Heating

Unlike traditional furnaces, which constantly operate at their full heating capacity, two-stage furnaces operate like two separate furnaces to maintain more consistent heating throughout your home. The first stage consists of the furnace running at about 68% of its heating capacity (enough to warm a home on mild winter days) and then adjusting itself to the second stage when temperatures drop in the home.


Furnace warranties vary according to the manufacturers and HVAC companies. Look for a good warranty, such as a 20-year limited warranty on the heat exchanger and a 5-year limited warranty on all remaining covered components. More efficient furnaces usually have longer warranties than basic models.

Your HVAC Partner

To ensure correct sizing and a proper installation, choose a reputable, licensed, and insured contractor who is certified by North American Technician Excellence (NATE) to calculate your heating needs according to an industry standards. At Atlanta Air Care, our technicians meet all of these criteria and we will also work with you to regularly maintain your furnace according to manufacturer recommendations after installation.