How long should an HVAC system last?
A well-maintained gas furnace typically lasts 15 to 20 years. Central air conditioning systems generally run 12 to 17 years. Heat pumps fall in the 10 to 15 year range depending on how hard they work in both heating and cooling seasons.
In Southeast Michigan — where furnaces run hard from October through April and AC systems pick up the baton in June — systems on the lower end of those ranges are common. The climate is demanding and it accelerates wear.
If your system is approaching or past these ages, a replacement estimate is worth having even if it is still running. Knowing the cost helps you make a smarter decision when the system does fail — instead of making a rushed choice in the middle of a Michigan cold snap.
The 8 signs your system needs replacing
Your system is 15 or more years old
Age is the most reliable predictor of imminent failure. A furnace or AC that has been running for 15-plus years is operating on borrowed time regardless of how well it has been maintained. Modern systems are significantly more efficient than equipment manufactured before 2010 — replacing an aging system typically reduces heating and cooling costs by 20 to 40 percent.
Your energy bills have been climbing
If your gas or electric bills have been rising over several years without a change in usage habits, your system is losing efficiency. Aging heat exchangers, dirty burners, refrigerant leaks, and worn compressors all force the system to work harder to deliver the same output — and you pay for that extra work every month.
You have had multiple repairs in the same season
One repair every few years is normal for an aging system. Two or more repairs in a single heating or cooling season is a strong signal the system is failing. Repair costs compound quickly — and paying $800 to repair a system that needs $3,000 in additional repairs over the next two years is rarely the better financial decision.
Some rooms are comfortable, others are not
Uneven heating or cooling throughout your home — some rooms too hot, others consistently cold — often indicates the system can no longer distribute conditioned air effectively. This can signal a failing blower motor, a compressor that is losing capacity, or duct issues that have developed over time. When an aging system can no longer maintain even comfort, replacement is usually the right call.
The system runs constantly without reaching the set temperature
A furnace or AC that runs all day without reaching your thermostat's set point is either failing internally, losing refrigerant (for AC systems), or was never correctly sized for your home. None of these conditions improve on their own — and the energy cost of a system running continuously is significant.
You hear unusual noises at startup or during operation
Banging, rattling, or popping at startup often indicates a cracked heat exchanger, loose components, or failing motor mounts. Grinding during operation can signal a worn blower motor bearing. A yellow or flickering pilot light on a gas furnace (it should burn solid blue) can indicate a carbon monoxide issue that warrants immediate attention — and often replacement.
Your AC uses R-22 refrigerant
R-22 (Freon) has been phased out of production and is now expensive and scarce. If your air conditioning system uses R-22 and develops a refrigerant leak, the cost of recharging it is often close to or exceeds the cost of replacing the system with a modern R-410A or R-454B unit. If you are not sure which refrigerant your system uses, it is usually printed on the data plate on the outdoor condenser unit.
Your next repair cost is 50% or more of a new system
A common rule in the HVAC industry: if the cost of the next repair exceeds 50% of the cost of a new system, replacement is almost always the better investment. A new system comes with a manufacturer warranty, improved efficiency, and years of reliable operation. A repaired aging system comes with none of those.
Repair or replace — how to decide
A quick decision framework
Lean toward repair if
- System is under 10 years old
- Repair cost is under 30% of replacement cost
- No other signs of system decline
- System has been well maintained
- Only one repair needed
Lean toward replacement if
- System is 15 or more years old
- Repair cost is 50% or more of replacement
- Multiple signs of decline present
- Energy bills have been rising
- Multiple repairs in the same season
The cost of waiting until failure
The biggest risk of waiting until a system completely fails is timing. Furnaces fail in the coldest weeks of a Michigan winter — which is also when HVAC contractors are at their busiest. Emergency installation slots fill quickly, and the pressure to decide immediately rarely leads to the best equipment choice or the most competitive price.
Planning a replacement on your timeline — rather than your furnace's timeline — means more time to get multiple estimates, choose the right system, and schedule at a time that is convenient for you.
Our recommendation: If your system is 12 or more years old and showing any of the signs above, get a replacement estimate now — even if the system is still running. A written quote costs nothing and gives you the information you need to make a good decision before a Michigan cold snap makes it for you.
