Are New Furnaces More Efficient?

Why Are Old Furnaces Less Efficient?

Older furnaces are significantly less efficient than modern units due to outdated technology, wear and tear, and evolving energy standards. Here’s why older heating systems fall behind in efficiency:

1. Lower AFUE Ratings in Older Models

In the past, AFUE standards were much lower than today’s requirements. Furnaces built before 1992 typically had AFUE ratings of 60-70%, meaning up to 40% of fuel was wasted. In 1992, the U.S. Department of Energy (DOE) mandated a minimum AFUE of 78% for new furnaces. By 2015, the standard rose to 80% for non-condensing furnaces and 90%+ for condensing models.

2. Heat Loss Through Exhaust and Combustion

Older furnaces waste energy due to inefficient combustion and outdated venting systems. Many older models use a single heat exchanger and vent hot combustion gasses out of the home. Modern condensing furnaces have two heat exchangers which capture and reuse heat from combustion gasses to reduce waste. Older models also use open combustion, pulling in air from inside the home, while modern furnaces use sealed combustion, drawing air from outside to improve efficiency and safety.

3. Loss of Efficiency Over Time

Even if your furnace was efficient when it was new, efficiency naturally declines over time due to:

• Wear and tear on components: Burners, heat exchangers, and blowers degrade over time, reducing performance.
• Dirty or clogged filters: Restricted airflow forces the furnace to work harder and causes more wear to the system.
• Slower ignition systems: Older pilot lights waste gas, while modern furnaces use electronic ignition to improve efficiency.

If your furnace is more than 15 years old, it is likely operating at a much lower efficiency than when it was first installed, even if you’ve stayed on top of regular maintenance.

Furnace Efficiency by Type

Are new gas furnaces more efficient? Are new electric furnaces more efficient? Are new oil furnaces more efficient? Furnace efficiency varies depending on the type of fuel it uses. Modern gas, electric, and oil furnaces have all improved significantly in energy performance, but each has unique advantages and drawbacks. 

Are New Gas Furnaces More Efficient?

Gas furnaces remain the most popular heating choice due to their balance of efficiency, performance, and cost-effectiveness. Modern gas furnaces have AFUE ratings between 80-98%, which is a huge improvement over older 60-80% models.

One of the biggest benefits of a new gas furnace is lower energy costs, as natural gas is often more affordable than electricity in many areas of the country.  High-efficiency condensing gas furnaces use a secondary heat exchanger to extract more heat from combustion gasses for greater efficiency.

Despite their efficiency, gas furnaces still contribute to carbon emissions since they burn fossil fuels, making them less environmentally friendly than electric models. They also come with a higher upfront cost and require access to a natural gas line, which can be a significant obstacle for homes without an existing hookup.

Are New Electric Furnaces More Efficient?

Electric furnaces operate with an AFUE of 100%, meaning they convert all electricity into heat without any waste. This makes them the most thermally efficient option. However, efficiency alone doesn’t tell the whole story – electric furnaces can be more expensive to operate due to electricity costs.

Since electric furnaces don’t rely on fuel combustion, they produce zero emissions and there’s no risk of carbon monoxide exposure. Because electric furnaces don’t experience the same wear and tear as combustion-based heating systems, they often last 20 to 30 years with minimal upkeep.

While new electric furnaces are 100% efficient in energy conversion, their high operating costs can make them less cost-effective in the long run. Electric furnaces also tend to heat more slowly than gas systems, which can make them feel less responsive in cold weather. In extreme winter conditions, they may also struggle to keep up with heating demands.

Are New Oil Furnaces More Efficient?

Oil furnaces are less common today but are still used in some regions without natural gas access. Older oil furnaces had AFUE ratings of 60-80%, while new models now reach 85-95% efficiency.

New oil furnaces burn fuel more cleanly, so they waste less fuel while delivering better performance. They also produce intense heat which means they offer hotter air than both gas and electric furnaces to warm homes quickly and effectively. 

Heating oil is often more expensive than natural gas, leading to higher fuel costs over time. Another factor to keep in mind is that oil furnaces require an on-site storage tank, which must be maintained and refilled regularly. Oil heating systems also need more maintenance than gas or electric furnaces to prevent soot buildup and keep the system running efficiently.

Weighing the Pros and Cons of High-Efficiency Furnaces

High-efficiency furnaces offer great benefits, especially when it comes to reducing energy costs. With an AFUE rating of 90% or higher, these furnaces convert more fuel into heat, meaning less waste and lower heating bills over time. They’re also eco-friendly, producing fewer emissions, and they tend to last longer, saving you money on repairs in the long run.

That said, high-efficiency furnaces come with a higher upfront cost. The initial price and installation can be significantly more expensive than a standard 80% efficient model. If you're on a budget, an 80% furnace can still do the job well, especially for homes that don’t need constant heating. While it won’t save you as much on energy bills, it’s a more affordable option if you’re looking to balance cost with performance.