The 4 Signs a Home’s Central Air Is On Its Way Out, According to Experts

The average lifespan of central air conditioners is about 15 to 20 years, according to the U.S. Department of Energy. But if you live in a city where summers are scorching hot and you don’t want your AC to retire on one of those 100-degree days, you may be curious: What are some telltale signs that your air conditioning unit is about to lose its cool?

I asked a home inspector and HVAC expert about how to gauge the condition of a central air unit. They also shared tips to keep your air conditioner in tip-top shape to help extend its lifespan. 

If you’re a homebuyer and trying to determine how old an AC unit is at a prospective home, you can look at the name plate attached to the condenser unit (which is the outdoor component with the fan), says Mike Powell, a home inspector and structural engineer who owns Red Flag Home Inspection in Tampa, Florida. 

If the unit doesn’t have the date or you can’t find it, jot down the brand, model, and serial number and you can look online to figure out its age. Also worth noting: The International Association of Certified Home Inspectors has a more conservative estimate of the lifespan of air conditioners, which they put at between seven and 15 years and even less in places where AC units run more frequently (i.e. the lifespan is five to 12 years in Florida).

When you’re house hunting, one of the best ways to determine if an air conditioner is working properly is to be in the space during the peak cooling times of the day and see if the conditions are comfortable throughout the house, Powell says. 

“Inefficient and aged systems may adequately cool the space and dehumidify the air, but at the expense of running most of the time,” he says.

During a home inspection, professionals will do a more high level evaluation of the air conditioning equipment, taking measurements of the return versus the supply air temperatures and looking at temperature, humidity and dew point temperature readings, Powell explains.

If you pay attention, your AC unit may be giving some signs that it’s petering out. Here are some signs to look for, according to Walter Bennett, a Richardson, Texas-based HVAC expert with Green Leaf Air.

1. The air coming out of the vents is warmer than usual.
2. You hear strange banging or clicking noises from the unit.
3. You notice a musty smell when the central air is on.
4. Your electric bill has gone up lately or you see an increase in power usage on your electric bill. 

One of the best things you can do to keep your central air in good condition is keep the coils free of dirt, dust, and debris, says Powell. 

“When debris clogs the coils, efficiency is lost in the transfer of the cooling energy of the coils to the air,” he says.  

You also want to keep your filters clean and replace them every three months, says Bennett. Dirty filters slow down the air flow and make your unit work harder than necessary. Common filter locations are in walls, ceilings, or in the air conditioner itself.

Another tip: Routine air conditioner maintenance should be performed a couple of times a year. A professional service technician should be able to check for refrigerant leaks, locate any seal duct leakage, and pinpoint any wear and tear that needs addressing.