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Does an HVAC System’s Efficiency Rating Really Matter?

When shopping for a new heating and air conditioning system, a couple of factors to consider are the heating and cooling units’ efficiency ratings. You’ll also notice that the higher the efficiency ratings, the more efficient the system is supposed to be. But are these numbers the ultimate factors that determine how efficient a heating and cooling system is–and how much money you’ll save?

An HVAC System’s Efficiency Rating Does and Doesn’t “Matter”

While efficiency ratings can help you determine how efficient a heater or air conditioner is compared to others, in “real life” there are multiple factors that can affect how efficiently your system operates, such as the condition of the ductwork and how frequently you maintain the equipment. Below, we’ll get into a bit more detail about how efficiency ratings work and what else you need to consider before spending extra money on a high-efficiency system.


Let’s break down the basics about heater efficiency ratings and air conditioner efficiency ratings.

Heating Systems and AFUE

AFUE (Annual Fuel Utilization Efficiency) is the ratio used to measure the efficiency of furnaces and boilers. This ratio represents how efficiently your heater converts fuel into usable heat throughout the course of a typical year. AFUE is often presented as a percentage.

Currently, federal standards require all new furnaces’ AFUE to be 80% or higher. But what does an “AFUE of 80%” mean? Think of it like this:

  • You have 100% of a fuel (like gas or oil) to start.
  • If the furnace has an AFUE of 80%, it will convert 80% of that fuel into usable heat for your home.
  • The other 20% goes to waste due to heat loss and other factors.

As you can see, the higher a furnace’s AFUE, the less fuel it will waste.

Air Conditioning Systems and SEER

SEER (Seasonal Energy Efficiency Ratio) is the ratio used to measure the efficiency of air conditioners. This ratio represents the relative amount of energy the unit needs to provide a specific cooling output. In other words, the higher a system’s SEER is, the more efficiently the system uses energy.

As with AFUE, there is a federal minimum SEER, which has increased to 14. This is quite a jump compared to many older systems still in operation with SEERs only around 8.

Do HVAC Systems Always Perform at Their Efficiency Ratings?

Short answer: no. The efficiency rating is fluid throughout a given year. Sometimes your system will perform lower than, at, or higher than its efficiency rating. Think of the AFUE and SEER as more of a yearly average.


While owning a high-efficiency heater and air conditioner can save you money in the long run on your annual heating and cooling costs, many factors can undermine your system’s efficiency.

Lack of Maintenance

The Department of Energy recommends maintenance for both air conditioners and heating systems to prevent your system’s efficiency from going downhill. Also, routine preventative maintenance performed by a licensed HVAC professional is often a requirement for the manufacturer to honor their warranty, should something go wrong with your system.

Leaky Ductwork

If your ductwork is decades old, or if it has never been professionally sealed, you could be losing a lot of heat and conditioned air through gaps and rips. If your current system is less than ten years old and is struggling to make your home comfortable, you may want to have a professional test your ducts before you spend money on an HVAC system replacement.

Outdated Insulation

Your ductwork is typically located in your home’s attic and walls and sometimes the crawl space. Without adequate insulation in these areas, you can end up with a lot of heat loss during winter and heat gain during summer. If you own an older home, it can be extremely worthwhile to update your insulation. You’ll have a more comfortable home, and your HVAC system won’t have to work as hard or wear out as fast.

Incorrect Equipment Sizing

Getting HVAC units with the right capacity to heat and cool your home is paramount. If the equipment is “too big,” it will run for cycles that are too short to even heat or cool your home. If the equipment is “too small,” it will have to run for long cycles that can overheat the components and lead to frequent breakdowns.

When looking for an HVAC system replacement, consult a reputable HVAC contractor that will take the time to come to your home, examine its size and layout, and listen to your current heating and cooling challenges. This will help them determine what size range will be ideal for maximum efficiency in your particular home.

At Premier Indoor Comfort Systems, LLC, we offer only top-quality products and handle a full range of heating and air conditioning services in Canton and Tyrone, Georgia and Whittier, North Carolina. Contact us today online or give us a call at (770) 268-2422.