Shopping for furnaces can be confusing. If you know you need a new furnace, it’s good to be proactive and start your search before your furnace stops working. You might have already started scouring the internet. If so, you’ve probably noticed that furnaces come with percentages attached. One furnace may have 80% AFUE attached to its name and another will have 90% AFUE attached. All of these numbers may have left you scratching your head. What does this mean and how can you decide which is best for you?
What Is AFUE anyhow?
AFUE (Annual Fuel Utilization Efficiency) is a type of percent rating that indicates how much of the heat goes toward heating your home and how much is wasted. For example, if the rating is 80% then 80% of the energy is in your home, while 20% is wasted. If the rating is 90%, then 90% goes toward heating your home and 10% is wasted. Keep in mind, you pay for 100%. The rating lets you know what is wasted and what your home will actually use.
At this point, you may be wondering why anyone would ever choose the 80% rating if they have to pay for 20% waste. While most people would prefer their heating systems to be the most energy-efficient possible, it does come with a higher price tag. Higher efficiency furnaces are more expensive, but the energy savings can outweigh the initial cost.
Differences and Options of 80% and 90% Furnaces
As mentioned above, the 90% furnace has a higher price tag because it has more efficient technology. With an 80% furnace, the lost 20% of heat energy is exhausted through the furnace’s vent to the outside. A 90% furnace has a secondary heat exchanger to recover these lost gases which then diverts the gases into a condensing phase. This process retains more heat and lowers your energy bills.
Let’s take a look at the different options or features that are available on today’s 80% furnaces. The basic single-stage 80% furnace uses a single-speed, on/off blower motor and a burner that runs at full output. With an 80% furnace, once a house is warmed, the blower turns off. It then comes on again when the house isn’t warm enough. It also moves the air at one speed, which is unnecessary to maintain an already warmed home. Cycling on and off at one speed is not the most efficient or comfortable way to heat a home. Also, the 80% furnace burner operates at full output which is fine on the coldest days but wasteful during warmer temperatures. There are more efficient 80% furnaces that offer two-stage heating, and some have high-efficiency blower motors that can save you money on electricity; as well as, create more even temperatures in the home.
The 90% furnace is more efficient because it burns gas more efficiently, but there are many more options available to save energy and increase home comfort. Many of these models offer an electronically commutated blower motor or ECM, which runs continuously at variable speeds and heats the house more consistently. It creates more even temperatures in the home, which in turn uses less energy. Whenever a heating (or air) system cycles on and off it is using more energy than running continuously at a lower speed. A 90% furnace that utilizes a two-stage burner can save you money over a single-stage furnace that runs at full output. The two-stage burner will fire at a lower output and only fire at full fire rate when needed. This will help conserve energy and increase your comfort.
Basic Differences in Today’s Furnaces:
- 80% or 90% Single-Stage Heating Furnace (One-stage heat means it operates at full fire on or off) These are typically your less efficient for energy savings and comfort.
- 80% or 90% Two-Stage Heating Furnace (Two-stages of heat means it has a low fire and high fire operation) The furnace will typically run at a lower fire rate to save you money, and it will switch to high fire rate if needed.)
- 80% or 90% + Two-Stage Variable Speed Heating Furnace (Same as the two-stage above), but you have a higher efficient motor that is quieter, saves you money, and increases your comfort by evening out temperature swings in the home.
- 80% or 90% + Modulating Variable Speed Heating Furnace (The heating output modulates to meet the exact heating needs of your home.) These are your top of the line furnaces today with efficiency, quietness, and overall comfort.
Talk to a Professional at American Air Heating & CoolingYou may be wondering why anyone would buy the 80% furnace over the 90%, but for many, the higher price tag is reason enough. There may even be installation issues to consider as well. This is why you should contact your certified HVAC technician at American Air to go over the pros and cons of each and help you make the right choice for your heating needs and your budget.