How to replace your furnace
Choose the right size and features
In addition to examining efficiency, you also need to get the right-size furnace. Don’t assume your existing furnace is the correct size.
Online calculators from furnace manufacturers can roughly estimate what size your home needs.
A trained professional, however, can perform a detailed analysis that looks at how much heat your home needs given its insulation, number of windows and heat generated by lights and appliances.
Choose a furnace that’s too small, and your house won’t get enough heat. If it’s too big, your furnace will constantly cycle on and off, which wastes energy, wears out the furnace faster, doesn't provide a consistent temperature and can be annoying.
If (and only if) you have allergies, asthma, lung disease or other respiratory problems, you might want a higher-end model that improves your indoor air quality by using an electrostatic filter or high-efficiency particulate arresting (HEPA) filter.
Models with variable-speed blowers and variable heat output can be quieter and keep heat levels more consistent.