AFUE Ratings Guide

If you’re thinking about upgrading your furnace, one of the first steps is to settle on an efficiency rating. This will impact your up-front costs and what you pay for home heating in the future. Use this guide to learn more about AFUE ratings and how they affect you. 

What Is an AFUE Rating? 

AFUE stands for Annual Fuel Utilization Efficiency. It is a measure of how efficiently a furnace or boiler changes fuel into heat for your home within a year. The higher the AFUE rating (on a scale of 0% to 100%), the more efficient the system is at converting fuel into usable heat. 

How Is AFUE Measured? 

AFUE ratings are measured by calculating the ratio of a furnace’s heat output to the fuel it consumes in the process. This calculation accounts for the energy lost through exhaust gases, radiation and other factors that reduce efficiency. The result is expressed as a percentage, representing the proportion of fuel converted into heat. 

Figuring out a furnace or boiler’s AFUE rating involves conducting a conventional test cycle to measure the heat output and fuel consumption. This test cycle is designed to simulate typical heating conditions over the year, including both on and off periods. The heating system operates at full capacity for a prolonged period to establish its peak performance. 

What Is the Minimum AFUE Rating in 2023? 

The U.S. Department of Energy (DOE) has gradually increased HVAC efficiency ratings over the past few decades in an effort to promote energy efficiency and reduce greenhouse gas emissions. In 2023, the minimum rating for new gas furnaces changed to 81 AFUE. From 2015 to 2022, the South and Southwest regions had a minimum rating of 80 AFUE, and the North required furnaces to be rated 90 AFUE or higher. Better AFUE ratings cut down energy consumption, lowers utility bills and reduces the environmental impact of heating your home. 

Why Do Gas Furnaces Jump from 80 to 90 AFUE? 

When shopping for new furnaces, you may notice many models around 80 and 90 AFUE, and not a whole lot else to consider. This is because the technology required to exceed 80 AFUE causes a significant rise in performance. 

The 80 AFUE threshold has been the minimum requirement for gas furnaces in the U.S. since the 1990s. At this level, furnaces turn 80% of the fuel they consume into heat, with the remaining 20% sacrificed to the atmosphere through the flue. 

Gas furnaces must incorporate more advanced technology to secure higher AFUE ratings, such as two-stage or modulating gas valves, variable-speed blowers and secondary heat exchangers. These technologies help the furnace extract heat from the fuel source more effectively, boosting efficiency from 80 to 90 AFUE or higher. Today’s best furnaces cap out at approximately 98.5 AFUE. 

How Do AFUE Ratings Affect Furnace Costs? 

The cost of a furnace with a higher AFUE rating is normally higher than that of a lower AFUE-rated furnace. After all, more advanced technologies come with a higher price tag. The exact cost difference depends on the furnace brand, size and efficiency rating. 

When evaluating the up-front cost of a more efficient furnace, remember the long-term energy savings that awaits you. The real chance to save money on energy bills for the next decade or longer helps you to recoup the extra up-front investment. 

Is It Smart to Buy a Furnace with the Highest AFUE Rating Possible? 

Although a higher AFUE rating results in better home heating and lower energy bills, this doesn’t necessarily mean everyone should buy a 95 AFUE furnace. Below are a few factors to take into account when comparing costs and efficiency ratings:  

  • Climate: The colder the weather, the more frequently your high-efficiency furnace runs, and the sooner it will provide a return on investment. Therefore, higher AFUE ratings are most beneficial in cold climates that require more heating than cooling to sustain a comfortable indoor temperature. 
  • How long you’ll live in this home: If you picture living in your home for many years, purchasing a high-efficiency furnace may be a wise investment since it will pay for itself over time in energy savings. On the other hand, if you plan to move in the near future, the extra cost of a higher AFUE-rated furnace may not be worth it. 
  • Fuel costs: The impact of an efficient furnace is more evident when the price of fuel is higher. You’ll experience noticeable savings when your furnace converts a higher percentage of fuel into usable heat for your home. 

Consider a New Furnace Today 

For help determining the best heating system for your needs and budget, turn to Aramendia Plumbing, Heating and Air. We can help you figure out the up-front costs and long-term benefits of different AFUE ratings to guide your decision. We’re so confident you’ll be satisfied with our services that we offer a 100% satisfaction guarantee! To find out more or to schedule a free furnace installation estimate, please get in touch with a Service Experts office near you

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