Understanding Gas Furnace Efficiency Ratings: A Comprehensive Guide.

Gas furnaces are rated based on their energy efficiency, which is measured by the annual fuel utilization efficiency (afue). The afue rating tells you how efficiently a furnace uses fuel, with higher ratings indicating greater efficiency.

Gas furnaces are a popular choice for heating homes in colder climates, but how do you know which furnace is the most energy-efficient? To answer that question, you’ll need to understand the energy efficiency ratings of gas furnaces. Gas furnaces are rated based on their annual fuel utilization efficiency (afue), which measures how efficiently a furnace uses fuel.

The afue rating is expressed as a percentage, with higher numbers indicating greater efficiency. In this article, we’ll take a closer look at the different energy efficiency ratings for gas furnaces and what they mean for your home heating needs.

Understanding Gas Furnace Efficiency Ratings: A Comprehensive Guide.

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What Are Gas Furnace Efficiency Ratings?

Understanding Gas Furnace Efficiency Ratings: A Comprehensive Guide

When it comes to purchasing a gas furnace, understanding its efficiency rating is crucial. Efficiency ratings serve as a measure of how well your furnace uses fuel. We’ll take a closer look at gas furnace efficiency ratings, so you can make an informed decision when selecting a furnace for your home.

Explanation Of Afue (Annual Fuel Utilization Efficiency) Rating

Afue (annual fuel utilization efficiency) rating is the standard used in north america to measure furnace efficiency. This rating measures the amount of heat that your furnace produces compared to the amount of fuel used. The higher the afue rating of your furnace, the more efficient it is.

Here are some essential points to remember about afue ratings:

  • Afue ratings range from 80% to 98.5%.
  • An afue rating of 80% means that for every dollar spent on fuel, 80 cents worth of heat is produced.
  • Furnaces with higher afue ratings typically cost more upfront but have lower operating costs.
  • Regular maintenance of your furnace can help keep its afue rating at peak performance.

Explanation Of The Percentage System Used In Europe

In europe, the percentage rating system is used to calculate furnace efficiency. This rating measures the amount of fuel that your furnace uses to produce a specific amount of heat. The higher the percentage rating, the more efficient your furnace is.

Here are some essential points to remember about percentage ratings:

  • Percentage ratings range from 70% to 95%.
  • A percentage rating of 70% means that 70% of the fuel is converted into heat.
  • Furnaces with higher percentage ratings typically cost more upfront but have lower operating costs.
  • Regular maintenance of your furnace can help keep its percentage rating at peak performance.

Comparison Of The Two Rating Systems

In north america, afue ratings are used to measure furnace efficiency, while in europe, percentage ratings are used. Both ratings serve the same purpose of determining a furnace’s efficiency. However, they are calculated differently.

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Here are some essential points to remember about comparing afue and percentage ratings:

  • An afue rating of 95% is equivalent to a percentage rating of 105%.
  • A percentage rating of 75% is equivalent to an afue rating of 80%.
  • Generally, both rating systems result in a similar efficiency rating for a furnace.
  • When purchasing a furnace, make sure to compare the rating systems to ensure you are comparing apples to apples.

Importance Of Understanding The Rating System When Purchasing A Gas Furnace

Understanding the rating system when purchasing a gas furnace is essential to ensure you get the most efficient furnace for your needs. Here are some reasons why:

  • High-efficiency furnaces can save you money on your heating bills.
  • A more efficient furnace has a smaller environmental impact.
  • A furnace with a higher rating may qualify for local utility rebates or tax credits.
  • Understanding the rating system will help you compare different furnace models and make an informed decision.

Understanding gas furnace efficiency ratings is crucial when purchasing a furnace. By knowing the rating system, you can identify the best furnace for your home, ensuring maximum efficiency and savings.

Factors Affecting Gas Furnace Efficiency

When looking at the efficiency of gas furnaces, several factors come into play. Understanding these factors can help you make informed decisions about your unit. Here are the key factors affecting gas furnace efficiency:

Size And Power Of The Furnace

The size and power of the furnace are crucial factors in determining its efficiency. If the unit is too large, it will consume energy unnecessarily; if it is too small, it will struggle to heat your home. Here are the key points to keep in mind about size and power:

  • The proper size of the furnace is based on the size of your home, not the square footage alone.
  • A furnace that is too big for your home will consume more energy, increase your energy bills, and create an uncomfortable temperature in your home.
  • Alternatively, a furnace that is too small will struggle to heat your home, resulting in increased energy consumption and higher utility bills.
  • Choosing the right size of furnace is essential to your comfort, utility bills, and the lifespan of the unit.

Quality Of Installation

The quality of installation plays a significant role in the efficiency of your furnace. Poor installation is a common cause of energy waste, high utility bills, and the need for frequent repairs. Here are the key takeaways for quality installation:

  • A reputable hvac contractor with adequate experience and licensing should install your furnace.
  • Proper installation includes accurate sizing, sufficient ductwork, and ensuring the unit is connected to the proper electrical and gas lines.
  • An hvac technician should test the unit after installation to ensure it is working correctly.
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Age And Maintenance Of The Furnace

Age and maintenance of the furnace can affect the unit’s efficiency. As a furnace ages, it may lose its efficiency, and problems with the unit may arise. Here are the key points to consider:

  • A well-maintained furnace operates more efficiently, has a longer lifespan, and requires fewer repairs.
  • Regular maintenance includes changing air filters, cleaning the furnace, and checking the unit’s efficiency.
  • An older furnace may not have the efficiency ratings that newer units have, leading to higher energy bills.

Type Of Fuel Used

The type of fuel used can impact the efficiency of your furnace. Natural gas is a common fuel source, but propane and oil are also used. Here are the key takeaways about fuel sources:

  • Natural gas is the most efficient and cost-effective fuel source for gas furnaces.
  • Propane and oil are also used, but they are not as cost-effective as natural gas.

Building Insulation And Airflow

Building insulation and airflow play a crucial role in the efficiency of your furnace. Heating your home requires the heat to move efficiently through the air and reach different areas. Here are the key factors affecting insulation and airflow:

  • Well-insulated homes reduce the amount of heat lost and increase the efficiency of the unit.
  • Proper airflow ensures that the heated air is distributed evenly throughout the home.
  • Clogged air filters can restrict airflow, leading to higher energy consumption and the need for frequent filter changes.

Understanding these factors helps you keep your gas furnace running efficiently. Consider employing an experienced hvac contractor to conduct an inspection and ensure your unit operates efficiently.

How To Improve Gas Furnace Efficiency

Gas furnaces are an essential component of many households, especially during the cold winter months. The efficiency rating of your gas furnace largely determines how much energy it consumes to heat your home. In this section, we’ll discuss how you can improve your gas furnace’s efficiency with regular maintenance and inspections, upgrading to a more efficient furnace or components, improving insulation and sealing air leaks, and making lifestyle changes to reduce energy consumption.

Regular Maintenance And Inspections

Proper maintenance and regular inspections are crucial to ensure that your gas furnace runs efficiently. Here are some key points to keep in mind:

  • Schedule an annual inspection with a licensed hvac technician to clean and inspect your furnace.
  • Replace the air filter every three months or as needed because dirty air filters significantly reduce the efficiency of your furnace.
  • Ensure that the ductwork is clean and adequately sealed to prevent air leakage.
  • Keep your home’s thermostat set at a consistent temperature.
  • Installing a programmable thermostat can help you regulate your home’s temperature more effectively.
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Upgrading To A More Efficient Furnace Or Components

If your furnace is over ten years old, it’s time to consider upgrading to a more efficient furnace model. Here are some key points to consider:

  • Look for a furnace model with a higher afue (annual fuel utilization efficiency) rating, preferably above 90%.
  • An energy-efficient furnace might cost more upfront, but it offers long-term energy savings and reduces co2 emissions.
  • Consider upgrading other components like the blower motor to avoid energy waste and improve indoor air quality.

Improving Insulation And Sealing Air Leaks

Poor insulation and air leaks account for a significant energy waste in most households. Consider the following tips to improve insulation and reduce air leaks:

  • Check for air leaks around windows, doors, ductwork, and electrical outlets. Seal them with caulk, weather-stripping, or spray foam insulation.
  • Insulate your attic, walls, and basement to reduce heat loss. Good insulation can save you up to 10% on your energy bills.
  • Upgrade your windows and doors to energy-efficient models. They offer better insulation and reduce air leaks.

Making Lifestyle Changes To Reduce Energy Consumption

You can reduce your energy bills by making some simple lifestyle changes. Here are some key points:

  • Turn off lights, fans, and electronics when not in use to reduce energy consumption.
  • Program your thermostat to lower the temperature when you’re away from home, which can save you up to $180 annually.
  • Use energy-efficient appliances and light bulbs to reduce energy consumption.
  • Consider using a clothesline instead of a dryer.

By following these simple steps, you can improve your gas furnace’s efficiency, save money on energy bills, and reduce your carbon footprint.


As we conclude our discussion on understanding the energy efficiency ratings of gas furnaces, it is clear that we must prioritize our energy consumption to reduce carbon footprint and save money. Energy-efficient furnaces, with their high afue ratings, minimize greenhouse gas emissions and translate into lower utility bills, making them a smarter investment in the long run.

Homeowners should consider replacing their older and less efficient furnaces with models that have higher afue ratings to optimize their heating systems and improve their energy efficiency. We must endeavor to make informed choices when it comes to our heating requirements while considering the environment and our finances.

By being aware of the various energy efficiency ratings and their impact on our lives, we can make a significant contribution towards building a sustainable future for ourselves and the planet. Let us make a conscious effort to reduce our carbon footprint and promote energy efficiency.


I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.