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What is a Furnace's AFUE Rating, and Which Is Best For My Home?

Updated: Aug 4, 2023

Choosing the right energy efficiency level for your furnace is an important decision when it comes to purchasing new heating equipment. Furnaces are rated based on their AFUE (Annual Fuel Utilization Efficiency) number, which measures their efficiency in converting fuel to energy. A higher AFUE rating indicates a more efficient unit, resulting in potential energy savings.

There are three categories of furnace efficiency:

  1. Low efficiency, standard efficiency, and high efficiency. Low-efficiency furnaces (approximately 55% to 78% AFUE) are no longer in production.

  2. Standard efficiency furnaces, with an AFUE rating of around 80%, are the most basic models available today.

  3. High-efficiency furnaces are rated at 90% AFUE or higher.

When comparing 80% and 95% efficient furnaces, there are several factors to consider. An 80% furnace utilizes 80% of the fuel for heat production, with 20% wasted. In contrast, a 95% furnace uses 95% of the fuel for heating, wasting only 5%. This efficiency difference can result in significant long-term fuel savings.

Both 80% and 95% furnaces provide reliable warmth, but there are slight differences in comfort levels. An 80% furnace with a single heat exchanger may provide a rush of hot air when it starts, while a 95% furnace with two heat exchangers offers a more gradual heating process for enhanced comfort.

In terms of noise, a 95% high-efficiency furnace with sealed combustion minimizes operational sounds. On the other hand, an 80% furnace with atmospheric combustion allows some noise to escape. Factors such as the furnace's location and the type of furnace (single-stage, two-stage, or variable-speed) can also impact noise levels.

While high-efficiency furnaces have a higher upfront cost than 80% furnaces, potential energy savings and available rebates can offset the price difference over the furnace's lifespan. Installation costs for both types of furnaces are generally similar, with some variations depending on venting requirements.

Additional factors that affect furnace efficiency include the stages of heat (single-stage, two-stage, or variable-speed operation) and airflow options. Modulating furnaces with variable-speed airflow offer the most efficient and consistent heating experience.

When making your furnace selection, it's important to choose a reputable HVAC manufacturer and work with a trusted heating and cooling company experienced in installing and servicing high-efficiency equipment.

Ultimately, if you plan to stay in your home for 5+ years, a 95% efficient furnace may provide the best long-term savings. However, for rental properties or homes slated for sale, an 80% furnace can still be a suitable choice. Consider your specific needs, budget, and energy savings potential when making your decision.

For all your gas furnace, heat pump, and air conditioning needs, contact the experts at Salmark HVAC Services. We offer free estimates and next-day installation, ensuring your HVAC replacement project is completed on time.


Salmark HVAC


Lemon, IL

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