80% vs 90% AFUE Furnaces: Which One Should I Choose?

When buying a new furnace to heat your home, there are several factors to consider: choosing the right brand, size, and efficiency. One common question homeowners face is whether to select a furnace with an 80% AFUE rating or one with 90% or higher. HVAC.com explains the pros and cons of each to help you make the best choice.

What Is an AFUE Rating?

Each furnace comes with an AFUE (Annual Fuel Utilization Efficiency) rating, which measures how efficiently a heating system converts fuel into heat. For example, an 80% AFUE furnace converts 80% of the fuel into usable heat, with the remaining 20% lost in the combustion process. A 90% AFUE furnace, meanwhile, converts 90% of the fuel into heat, wasting only 10%.

Pros and Cons of 80% vs 90% AFUE-rated Furnaces

When comparing an 80% AFUE furnace to a 90% AFUE system, the primary differences lie in their efficiency and operating costs. Let’s take a closer look at the pros and cons of each:

80% AFUE Furnace

Pros:

1. Lower Initial Cost: 80% AFUE furnaces are generally less expensive to buy and install than 90% models. Expect to pay about $1,500 to $2,000 less for an 80% efficiency system.
2. Simpler Technology: These furnaces use basic venting systems (typically a metal flue) and don’t require a secondary heat exchanger, making them easier and less expensive to install and maintain.
3. Good for Milder Climates: An 80% AFUE furnace can typically meet heating needs in moderate climates.

Cons:

1. Lower Efficiency: It only converts 80% of the fuel to heat, with 20% lost in the exhaust, which means 20 cents of every dollar you spend on heating is wasted. This results in higher energy bills, which can add up over time.
2. Missed Rebates and Tax Credits: 80% AFUE-rated furnaces do not qualify for any potential rebates from utility companies or HVAC tax credits from the federal government. For gas furnaces to qualify for a tax credit, they must have an AFUE of 97% or higher.
3. Environmental Impact: Lower-efficiency furnaces produce higher emissions which have a negative impact on the environment.

90% AFUE Furnace

Pros:

1. Higher Efficiency and Lower Energy Bills: It converts 90% of the fuel to heat, with only 10% wasted, making these furnaces significantly more efficient. Due to the increased efficiency, you’ll use less fuel to heat your home, which translates to lower utility bills.
2. Better for Colder Climates: In regions with harsh winters, the higher efficiency makes this furnace more effective at keeping heating costs lower.
3. Fewer Emissions: A 90% AFUE furnace is more environmentally friendly because it releases few emissions.
4. Increased Comfort: With features such as variable-speed blowers and multi-stage burners, high-efficiency furnaces provide more consistent heating with fewer hot or cold spots, creating a more comfortable environment. Variable-speed technology and sealed combustion chambers also make furnaces with at least a 90% AFUE rating quieter than less-efficient models.

Cons:

1. Higher Initial Cost: A 90% AFUE furnace typically costs more upfront than an 80% model, both in terms of equipment and installation.
2. More Complex Venting: It requires a more sophisticated venting system (often PVC) to handle the cooler exhaust gases, which can add to installation costs.
3. Potential for More Repairs: With increased complexity in design, there’s a higher potential for needing repairs or maintenance compared to simpler 80% models.

Determining the Efficiency of Your New Furnace

Along with the type of furnace, its make and model, and sizing, efficiency is one of the most important considerations when buying a new furnace. An 80% AFUE is ideal if you’re looking for a budget-friendly option and live in a region with mild winters where heating demand isn’t too high. Meanwhile, a 90% AFUE is the better choice if you want to reduce long-term heating costs, live in a colder climate, and don’t mind the higher initial investment.

If you’re still unclear about whether an 80% or 90% or greater AFUE-rated furnace is best for your home and budget, contact HVAC.com. Our technician advisors can walk you through your options and connect you with a reputable HVAC company in your area.