What’s the Difference Between Oil and Gas Furnaces? – Sobieski Services | DE, NJ, PA, MD

What’s the Difference Between Oil and Gas Furnaces?

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When investing in a new furnace, it pays to know as much as possible about the fuel that will be producing the heat. The most common fuel-burning furnace options are oil and gas. The following information will give you a brief introduction to the differences between oil and gas furnaces and should help you narrow down your choice of heating system.

Fuel Characteristics

Natural gas is a very common type of fuel that is usually readily available through a connection to a gas utility’s supply line. In this way, you can always have natural gas available as long as your utility bills are paid. Natural gas is flammable but has been safely used as a heating fuel for years.

Oil, sometimes called fuel oil, is also common, but you usually have to order quantities of oil as needed. Oil is most often stored in a tank in or near your building, and you have to monitor the amount of oil in the tank to be sure you don’t run out. Fuel oil is not highly flammable and must be atomized and mixed with air before it can be burned for heat.


Furnace efficiency is indicated by the unit’s Annual Fuel Utilization Efficiency, or AFUE rating. Higher AFUE numbers indicate greater efficiency. AFUE ratings reveal how much of the energy in the fuel burned by the furnace is turned into usable heat. An AFUE of 90, for example, indicates that 90 percent of the fuel’s efficiency becomes heat while the other 10 percent is lost.

You can find high-efficiency furnaces that burn both natural gas and oil. In general, oil produces more British thermal units (BTUs) than gas, but gas is considered more efficient.


For an initial purchase, an oil furnace will likely cost less than a gas furnace. Higher-efficiency models of both types will typically cost more than those with lower efficiency ratings. However, the advantages of a natural gas furnace usually outweigh those of an oil furnace, making it the better choice between the two.

In terms of fuel costs, oil prices can fluctuate significantly even over the course of a heating season. In contrast, natural gas prices (and global supplies) tend to stay relatively stable. If the overall cost of petroleum products remains low, then fuel oil prices will mostly likely follow that trend. However, high petroleum prices can be reflected in fuel oil prices. Gas furnaces are usually preferred because of the relative stability of fuel prices.


Since natural gas is a highly flammable substance, there are safety concerns with a gas furnace that you don’t have to address with a gas furnace. Gas leaks can create a situation in which fires or explosions could occur if the gas has the chance to ignite. Fuel oil by itself will not present such a hazard. Gas furnaces should be professionally installed to ensure all appropriate safety factors are considered and accommodated.

Leaks of gas and fuel oil can both be hazardous, however, and will require specialized attention to repair and clean up. Since both gas and oil are burned, they both create potentially harmful byproducts, particularly carbon monoxide. Fuel-burning furnaces of both types must be properly vented to ensure that carbon monoxide and other exhaust products are safely diverted to the outdoors.


Both gas and oil furnaces will require regular preventive maintenance to keep them working at their best. However, oil furnaces usually require more attention. For example, oil furnace combustion chambers will need regular cleanings to remove soot and other material. Since gas burns much cleaner than oil, a gas furnace will require less maintenance of this type.

Our goal is to help educate our customers about Plumbing, HVACR, Fire Protection, and Alarm Systems in Mechanical, Commercial, and Residential settings. For more information on choosing between an oil and gas furnace, and to view projects we’ve worked on, visit our website!

Image Credit: “Adam Ciesielski/FreeImages.com”

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