When you are shopping for a new heating system, you might notice that many heaters include an AFUE rating. This is an important specification that tells you a lot about the machine’s performance. To pick the best heater for your home, you will need to learn what AFUE ratings are and how they work.
What Does AFUE Mean?
AFUE stands for the Annual Fuel Utilization Efficiency ratio. This is essentially the percentage of heat your heater generates from the amount of fuel it has. Whenever a heater runs, most of the fuel will go towards generating heat. However, some of the fuel will be used to keep the furnace running.
Therefore, the AFUE helps to tell you exactly how much fuel is converted into heat for your home. It can be a very valuable way of measuring the overall efficiency of a heater. A higher AFUE will mean your system is more energy-efficient. You can usually find an AFUE rating by reading the yellow EnergyGuide tag on the appliance. If your heater doesn’t have one of these tags, you can check the owner’s manual instead.
How Does a Company Determine an AFUE Rating?
AFUE ratings are regulated by the American Society of Heating, Refrigeration, and Air Conditioning Engineers. This national standard is found by examining a machine’s operation. HVAC technicians determine an AFUE by measuring a furnace’s heat output in BTU and its fuel input in BTU. Then they divide the heat output by the fuel input to find the AFUE.
AFUE Vs. Thermal Efficiency Vs. HSPF Vs. SEER
AFUE ratings typically get confused with other common measurements for energy efficiency. Since one system can have multiple ratings, it is important to understand the difference between all the rating types. One of the most commonly confused things is AFUE and SEER. The Seasonal Energy Efficiency Ratio (SEER) rating is very similar to AFUE. However, it’s used for air conditioners instead of heaters.
The Heating Seasonal Performance Factors (HSPF) is another slightly similar energy rating. However, it measures overall energy transfer over the course of an entire heating season. HSPF is found by dividing the total heat output of a machine during a normal chilly season by the total heat input. It’s useful for seeing how efficient a machine stays while dealing with all the various temperature fluctuations of winter.
While AFUE does measure how efficient a machine is at producing heat, it’s not the same as thermal efficiency. Thermal efficiency is a technical term that measures how much work your system needs to produce a set amount of heat. Essentially, it measures how powerful a heater is. A heater with a high thermal efficiency rating produces more heat at any given time.
Which Heaters Use AFUE Ratings?
Whether or not AFUE matters usually depends on the type of heater you are looking at. Technically speaking, all heaters have an AFUE. However, AFUE ratings are mostly relevant for furnaces that run on fuel like oil, gas, or propane. The AFUE rating is an easy way to compare two similar models. It lets you know which model does a better job of turning fuel into heat for your house.
Meanwhile, electric furnaces always have an AFUE rating of 100. Since they convert 100 percent of their energy into heat, they are always as efficient as possible. The AFUE on an electric heater does not tell you much about the costs associated with running it. Another type of heater that does not really use AFUE is a heat pump. To compare the energy efficiency of these types of systems, you are better off looking at the heater’s HSPF or annual energy usage instead.
What Counts as a Good AFUE?
When it comes to AFUE ratings, higher is usually better. How high of an AFUE can you expect? It helps to know the typical AFUE range for standard types of heaters.
- Heating oil: 70%-89 %
- Electric: 100%
- Natural gas: 78%-84%
- Propane: 79%-85%
- Firewood: 45%-65%
Keep in mind that these are just averages. The absolute minimum AFUE required for new furnaces is 78%, but most tend to have an AFUE of around 80%. There are plenty of modern furnaces that have an AFUE of 90% or higher. Some high-efficiency systems may have a rating as high as 97%.
How Much Money Does a High AFUE Save?
Since an AFUE rating is a percentage, it’s easy to figure out just how much money you save. For every dollar that you spend on fuel, the AFUE rating is the amount in cents that will go toward heating. So, for example, with an AFUE rating of 80, you would spend $0.80 directly on heating and waste $0.20 on operating costs. This means that going up to a heater with an AFUE rating of 90 would save you $0.10 for every dollar spent.
The exact amount you save will depend on your local utility costs and the length of time you run your furnace. The typical homeowner saves around $250 per year by upgrading to a furnace with an AFUE rating 20 higher than their previous model. However, keep in mind that high-AFUE furnaces tend to cost more. Therefore, you might need to spend a little more to invest in a high-efficiency system in the first place. As long as you keep the same system for around 10 to 15 years, the extra savings on monthly bills will compensate for the cost and save you money in the long run.
When trying to find the most affordable furnace, you also need to take into account fuel costs. Certain types of furnaces, like electric furnaces, always have higher AFUE ratings. However, in some regions, it can cost more to get that sort of fuel. You might find that you save a little more by going with a lower AFUE model that burns a different type of fuel. Take the time to do the calculations and see what works best for your individual needs.
Does AFUE Affect Anything Besides Operating Costs?
When people look at high-efficiency heaters, their first concern is usually operating costs. However, efficient models do more than just save you money. For some homeowners, a big perk of a high-AFUE model is that it wastes less energy. This can make your home more sustainable and energy-efficient. Even if you don’t care about this personally, more eco-friendly homes tend to sell well. More efficient heaters also mean you end up with fewer combustion byproducts and vented heat. This can reduce your risks of dealing with inconvenient ventilation problems later on.
Ultimately, the AFUE rating has a lot to do with how well your system runs, but it’s not the only factor. Your system type, size, and layout can all have a big impact on how warm your house is and how much your energy bills cost. If you want to save as much money as possible, Gallagher's Plumbing, Heating and Air Conditioning can help. In addition to assisting with heater selection and installation, we can also maintain your system to keep it running as efficiently as possible. We provide a wide range of services to homes in the Greater Sacramento region, including HVAC repairs, installations, and maintenance. Schedule your appointment by giving us a call today.