What are the differences between gas and electric furnaces?

In this article, we review gas and electric furnaces, how each type of furnace works, and some of the key differences between them. If you need a new furnace in your home and you’re trying to decide between natural gas and electric models, call our team for a free in-home estimate today.

Gas furnaces

Gas furnaces generate heat for your home by combusting fuel (natural gas) in a combustion chamber and then transferring that heat to air through a heat exchanger.

A technician inspects a gas furnace after installation.

A technician inspects a gas furnace after installation.

Understanding gas furnace efficiency

When it comes to energy efficiency, gas furnaces are relatively efficient at generating heat for your home. The efficiency of a gas furnace is measured by its Annual Fuel Utilization Efficiency (AFUE) score. AFUE is the measure of how much heat a furnace can pull from the gas as it combusts it. A gas furnace with 80% AFUE converts 80% of its fuel into heat, with 20% being lost in the exhaust. In other words, the higher the AFUE, the more efficient a furnace is, as it will use less gas to produce more heat.

Today’s furnaces have an efficiency floor of 78% AFUE, but many high-efficiency models are nearing 100% AFUE. For example, the Carrier Infinity® 98 Gas Furnace boasts a 98.5% AFUE score, making it one of the most efficient furnaces on the market today.

An important note before we move on: AFUE is less useful when comparing different types of systems. As we’ll review below, electric furnaces have 100% AFUE, but that doesn’t make them less expensive to run. The same thing goes for propane or oil.

A system for all seasons

Because they draw heating energy from natural gas and not electricity, many gas furnaces do not need excessive amounts of electricity to operate. This makes them ideal during power outages caused by storms since they can be run off of a backup generator in your home.

Electric furnaces

Electric furnaces work like a super-sized hair dryer or toaster. Electric current is run through heating elements, heating them up to high temperatures. Cold air is then forced through those elements, rapidly heating the air before it is pushed out through your air ducts to the living spaces of your home. This process continues until the air temperature in your home matches what your thermostat is set to.

More efficient, but costs more to run

On the surface, this feels like a paradox, right? How can an electric furnace with 100% AFUE cost more to run than a gas furnace with 93% AFUE? While electric furnaces are far more efficient at converting their energy source (electricity) into heat than other types of furnaces, this efficiency is counterbalanced by the market prices of each energy source. Natural gas is typically far less expensive than just electricity, so even the most efficient electric furnaces may be more expensive to run.

Of course, the exception to this rule applies to homes with electric-generating solar panels. By pairing an electric furnace with rooftop solar, you can defray some of the costs associated with heating your home in the winter.

No need to vent

Unlike their gas-burning cousins, electric furnaces do not need to expel combustion gases from the home via a flue pipe. This means that an electric furnace only needs to be connected to ductwork, allowing it to go in more places in your home.

No gas combustion also means that electric furnaces do not have a flame sensor, a heat exchanger, or other components found in a gas furnace. There’s no risk of a gas leak or a carbon monoxide leak, although such events are relatively rare in a gas furnace, as well.

Other types of furnaces

There are also furnaces fueled by propane and oil. While these furnaces—like electric furnaces—are often more efficient than gas furnaces, their fuel types are more expensive. If you’re considering either of these types of furnaces, be sure to talk to your local HVAC company about energy costs in your area and what you can expect to pay to heat your home in the winter.

Learn more about gas and electric furnaces

If you’re deciding between gas and electric furnaces, calling us is actually a good place to start. At King Heating, Cooling & Plumbing, we offer free in-home estimates on new systems. Our technicians can meet with you to review your home’s heating needs, and then help you find the right system for your house and your family. Contact us today to schedule your free in-home estimate.