The US Department of Energy imposes efficiency standards on all products manufactured in the US. One example of that is the AFUE or Annualized Fuel Utilization Efficiency rating. Since nearly half of the energy consumed in US homes is attributed to heating and cooling, it is crucial to understand how AFUE ratings work and how to determine what appliances are worth investing in.

What are AFUE Ratings?

AFUE stands for Annualized Furnace Efficiency. This rating refers to the efficiency of the furnace over time. This ratio refers to the amount of fuel your furnace converts to energy utilized to heat your home. The amount of energy the furnace consumes will also determine how much you will pay on your energy bill.

The American Society of Heating, Refrigerating, and Air Conditioning Engineers created the AFUE rating. It became the standard that was adopted by the US Department of Energy. The rating ranges from 0 to 100% with the current minimum standard for efficiency set at 80%. This rating means that only 80% of the fuel is converted into heat while the other 20% is wasted or released through exhaust pipes. The standard AFUE rating is at least 83% but most high-efficiency furnaces have a rating of 90% or more.

When shopping around for a new furnace, look for a higher AFUE rating because it indicates a higher fuel efficiency. You can find the AFUE rating on the faceplate of the unit, or you can check the serial number.

How is the AFUE Rating Calculated?

The formula to calculate the AFUE rating is straightforward. The amount of fuel that is supplied to the furnace is computed with the amount of heat produced by the system. The AFUE rating uses BTU as the unit of measurement. The AFUE rating only refers to the average heat production and it can vary from day to day.

The formula for AFUE is total annual heat output / total energy input x 100.

For example, the total annual heat output is 80,000,000 BTUs and the total energy input is 100,000,000 BTUs. 

AFUE = 80,000,000 BTUs / 100,000,000 BTUs x 100 = 80%

Given the numbers above, the efficiency rating for the furnace is 80%, which is right within the minimum standard. 

Types of Furnaces

The US Department of Energy recommends buying furnaces with a high AFUE rating because it translates into higher efficiency. But is it worth it? 

It’s worth noting that the AFUE rating is only a suggestion. There is no one-size-fits-all approach when measuring the standard of various furnace types for home use. However, the ratings will give you an idea of how much energy is consumed and how effectively your home can be heated. 

A low-efficiency furnace typically falls within the 56-70% rating. This rating is common in single-stage furnaces, which switch on when your home is cold and turn off when at the desired temperature. It comes with a simple exhaust system that relies on the natural draft of your home without the capacity to adjust the blower speed.

A mid-efficiency furnace has an AFUE rating of 80 to 83%. It represents the majority of the furnace systems on the market. This furnace type costs between $900 to $1,800. A mid-efficiency furnace consists of an electric ignition or exhaust fan, and they are smaller in size. They come in single-stage and two-stage configurations. The latter provides better heating control than what is available with a low-efficiency furnace. 

Lastly, there are high-efficiency furnace models that you can distinguish because of their Energy Star label. Most high-efficiency furnaces have a 90-98% efficiency rating. These furnaces have a sealed combustion chamber that ensures your home stays warm with exhaust being emitted outside the home. This furnace system includes more advanced features, such as an advanced heat exchanger, variable blower, ignition, and a multi-stage heating configuration. Therefore, you can get more heating control and precision with high-efficiency models. It’s also why they are the most expensive model, with a price range of $3,000-$4,000. 

Benefits of High AFUE Rating

The primary benefit of investing in a high-efficiency furnace is that it costs less to run the system. It could translate to more energy savings in the long run. Furnaces with a high AFUE rating use less energy to generate heat and power the entire system. Therefore, it means lower energy bills in your home. The daily savings might not mean much, but these savings add up over time.

Although the initial cost of a high-efficiency model is higher than lower-efficiency models, you can get more value for money in the long run. High-efficiency models generate and utilize energy and heat, which won’t strain the system. As a result, they will last longer, and you can experience a higher return on investment. 

Factors that Impact Efficiency Rating

When shopping for a new furnace, the AFUE rating is the primary factor to consider as it determines the efficiency level of the system. However, consider other factors in choosing the right furnace. These factors can also impact the efficiency of a furnace and its capacity to heat your home with less energy and wasted heat.

The first factor that impacts furnace efficiency is the insulation of your home. It goes hand-in-hand with choosing a high-efficiency furnace model to ensure you can maximize the performance of the system. A well-insulated home can hold heat better than one without adequate insulation. Proper insulation means that the furnace won’t have to work as hard to keep your home warm because the heat cannot escape your home.

Before buying a new and high-efficiency furnace, make sure to properly insulate your home. Add insulation to the walls and attics. You can also invest in energy-efficient doors and windows to discourage heat from escaping outside. Other things to look into to maximize furnace efficiency are furnace filters, radiator placement, sealing entryways, updated ductwork, and a thermostat upgrade. 

In addition, you should consider the climate where you live. Some areas have colder climates, so you need a more efficient furnace to keep your home warm and comfortable. It also pays to invest in regular maintenance to keep your furnace running efficiently and save more money in the long run.