by Ali Kriscenski

Your building operations depend on the reliability and efficiency of your heating and cooling system. The type of furnace you choose is central to providing safe, consistent and comfortable conditions for occupants and equipment. In this article, we’ll take a look at the different types of furnaces and how to choose the right one for your facility.

How Furnaces Work 

An HVAC system consists of several components including fuel source, furnace, ductwork and controls. The furnace is the element that turns the fuel into thermal energy used for heating. The thermal energy is then distributed throughout a building via ductwork or radiation. The types of furnaces and how they work relate to the fuel source; for example, oil furnaces use a combustion process and electric furnaces use a heating element.

4 Types of Furnaces for Commercial Buildings

Choosing the right furnace for your facility depends on several factors including the building or facility size, the program of the space (industrial, office, retail, hospitality, etc), existing HVAC ductwork or other distribution, and your investment and operating budgets.

1.Natural Gas Furnaces

As a fuel source, natural gas or renewable natural gas (RNG) is a combustion fuel commonly used to produce heat for residential and commercial spaces. Natural gas is available worldwide with estimated stores that will meet the demand for 100 years. Additionally, new innovations for renewable natural gas are on the rise which will increase the availability of this fuel resource. Natural gas furnaces are cost-effective and newer units are highly efficient, up to 98%. 


2. Oil Furnaces

Oil furnaces are common throughout the U.S., and known as a more affordable option than natural gas furnaces in terms of upfront investment. They are slightly less efficient than natural gas furnaces, with efficiency between 80% and 90%. Oil furnaces can require higher maintenance than other types of furnaces because of the residue (or sludge) that can accumulate in the tank, lines, filters or burner. Oil storage tanks can rust and lead to leaks that require costly remediation. 

3. Electric Furnaces

One of the benefits of electric furnaces is their high efficiency, between 95% and 100%, and they typically last up to 20 years. Electric furnaces can provide consistent thermal comfort and are a wise choice for localized or condensed heating requirements. In an electric furnace, electricity flows to a heating element which raises the temperature of air that is then pushed out of the furnace. Electric furnaces are an economical upfront choice and although they can have higher operating costs, they have other benefits, like no carbon monoxide. 

4. Propane Furnaces

Propane furnaces work similarly to oil and natural gas forced air furnaces and provide an option for fuel availability in more remote or isolated locations where oil or natural gas are not available. Typically, propane costs are similar to oil, as propane is a byproduct of oil and natural gas production. Propane gas is delivered by container so the related transit costs are a variable in cost efficiency. Overall, propane is a clean and safe fuel source that has little environmental impact with 90% to 98% efficiency.


Considerations for Furnace Selection

When choosing the right furnace type for your facility there are a number of considerations to include: the cost of the furnace itself, the cost of the fuel used, venting requirements and the Annual Fuel Utilization Efficiency (AFUE), which indicates the efficiency of the furnace’s combustion. 

Factors that can be part of your selection process can include unit pricing, installation costs, fuel and operating costs. While some types of furnaces are affordable upfront, a higher operating cost over time may make them cost-prohibitive. Alternatively, a system that is only needed short-term makes operating costs a less relevant selection factor. 

In today’s HVAC market, there are continually evolving innovations that can make any system more efficient. For example, an electric furnace coupled with solar may create the most efficient, cost-effective investment instead of the same furnace grid-connected. Enlisting an HVAC expert like Therma can help you navigate all of the variables and system configurations to maximize your investment. 


Ali Kriscenski was trained in high-performance building design at Boston Architectural College. She has worked with leading architecture and construction firms in NYC and New England and served on the executive team at the Forest Stewardship Council International. She was the managing editor at Inhabitat and has worked pro bono for the Green Building Institute, ISEAL Alliance and Habitat for Humanity.


Science Direct – Natural Gas Overview

U.S. Department of Energy (DOE) – Furnaces and Boilers

HB HOME – Is an Electric Furnace an Energy-Efficient Option?

Propane – Propane Furnaces

Bob Vila – Gas vs. Oil: Which Furnace Is Better?