What is a furnace?

A household furnace is a major appliance permanently installed to provide heat to the interior of a home. An energy source heats air within the furnace, and then a fan blows the warm air throughout the house and pulls cooler air to the furnace. The air travels from the furnace to the rooms of the house through ductwork.

During the last one hundred years, home heating has changed and advanced. In the beginning there were Gravity Furnaces and Steam Heat Systems. 

Gravity furnaces had no fans; the furnace heated air, and used ductwork that sloped up from the furnace to the heat registers. The rising warm air would rise from the furnace, through to ductwork, to the rooms. Gravity heaters had very few moving parts, and could last fifty years or more. The central heating unit in a steam heat system is a boiler. It heats water until steam was produced, which is pumped through the building to radiators. Many older apartment buildings still use steam heat.

Following gravity heat and steam heat came forced air heat. Air was heated in the furnace using natural gas, coal, liquefied petroleum gas (LPG), fuel oil, coal, or electrical resistance. Warm air was then "forced" through the ductwork by a fan or fans. The early forced air furnaces delivered only 60% fuel efficiency.

Our discussion of the history of furnaces is not purely academic. If you are shopping for a furnace there is a good chance you have one of these older types of furnaces in your basement or garage that is either malfunctioning and/or contributing to high monthly energy bills.

Want to receive free estimates for your furnace project?

We have partnered with QualitySmith in order to allow our visitors to receive free, no obligation project quotes from qualified local contractors.  QualitySmith is a free, well regarded contractor referral service.

Click here to receive 3 free, no obligation quotes for your furnace project.

Should you buy a furnace?

There are two conditions that frequently cause home owners to consider buying a furnace: either the current furnace is not repairable or is requiring frequent repairs, or the furnace is contributing to high monthly energy bills. Rising fuel costs around the United States are making it easier to financially justify investing in a new, energy efficient furnace.

The United States Environmental Protection Agency (EPA) and the Department of Energy (DOE) have created a Life Cycle Calculator for estimating the savings you will get over time by investing in a more energy efficient furnace now.

In addition to the energy savings, there are other factors to become educated about and consider prior to making your furnace decision. This Furnace Buying Guide is here to help inform you about the factors you need to consider when making a purchase decision for a new furnace.

What's new about furnaces?

There are a number of new developments you'll find as you shop for furnaces:

Energy Efficiency: In 1992, the Department of Energy instituted strict new guidelines that all new furnaces need to convert 78% of fuel to energy. Compare that to the 60% fuel to energy conversion rates that were common at the time. Since then, manufacturers have met the requirements and gone beyond them. Furnaces are now available with energy conversions rates up to 96.7%. The market is now in two segments. 78% to 89.9% conversion rates are termed mid-efficiency furnaces, and higher than 90% conversion rates are high-efficiency furnaces. You can use the Life Cycle calculator provided in the “Should You Buy a Furnace?” section to calculate your savings from purchasing a mid-efficiency furnace compared to a high-efficiency furnace. We further discuss mid-efficiency furnaces and high-efficiency furnaces in the Factors to Consider section of this guide.

Programmable electronic thermostats: A programmable electronic thermostat gives you more control over when you heat your home. It can enable you to reduce the heat during the hours you are asleep and at work, and raise the temperature in the hour before you wake up or return from work. This means that you do not have to sacrifice comfort for energy efficiency. Studies show that using a programmable thermostat can save up to 33% on heating bills.

Zone Heating: Zone heating approaches heating your home on a room-by-room (or zone-by-zone) basis. The elements of a zone heating system are programmable thermostat, temperature sensors in each zone, registers that electronically open and close and are controlled by the system, and a furnace fan that is varies its speeds. The zone heating system uses information it gets from the sensors in the zones and the control it has over registers and fans to deliver heat on a room-by-room basis as needed. Unlike purchasing most furnaces, zone heating requires installation of new registers and sensors. While this approach can be more expensive up front, the energy savings from zone heating can be substantial, and a zone heating system results in a more comfortable home because it eliminates hot-spots and cold-spots.

Selecting a furnace

There are eight factors for you to consider when you are selecting furnace. We also show you four features that are commonly available in furnaces. If any of these features are important to you, you may choose to select only models with your favorite features.

Click here to see our selection of Top Furnace Brands