When your furnace stops working in January, the first question is always: repair or replace?The right answer in Brentwood, Franklin, or Spring Hill depends on three things - the age of the unit, the cost of the fix, and how the system has performed over the last 12 months.
The 50% rule, adjusted for Middle Tennessee
The industry rule of thumb is: if a repair costs more than 50% of replacement, replace. For Williamson County homes that's a decent starting point, but it ignores two local realities. First, gas is cheap here, so an older 80% AFUE furnace isn't bleeding you on operating cost the way it would in the Northeast. Second, our heating season is short - November through early March - so a borderline unit can often limp through one more winter without drama.
When repair is the right call
- Unit is under 12 years old. Modern furnaces are good for 18-20 years with maintenance. You have runway.
- Repair is under $600. Igniters, flame sensors, pressure switches, capacitors, gas valves - all repairable for less than a tank of refrigerant.
- The system has been reliable. One failure in a year isn't a pattern. Three is.
- You're staying in the home 5+ years. A new install pays back over a decade, not a year.
When to replace
- 15+ years old AND the repair is $1,000+. The next failure is coming. Budget for it.
- Heat exchanger crack. Non-negotiable. A cracked heat exchanger leaks carbon monoxide into the supply air. Replace.
- Repeat failures. Three service calls in 18 months means you've already paid for half a new system.
- R-22 paired AC. If the AC side runs R-22 and is also aging, the math usually favors replacing the matched set.
What furnace repair in Brentwood typically costs
Most Brentwood and Franklin furnace repairs land in three brackets:
- $150 - $400: Flame sensor cleaning, igniter, pressure switch, capacitor, thermocouple.
- $400 - $900: Gas valve, blower motor, control board, draft inducer.
- $1,000 - $2,500: Heat exchanger (rarely worth it on older units), full blower assembly, secondary HX on a 90%+ system.
Climate Pro members pay 15% less on every bracket above and skip the diagnostic fee entirely.
Don't skip the diagnostic
A real diagnostic on a no-heat call takes 30-45 minutes. We check the gas pressure at the valve, sequence of operation, flame signal in microamps, static pressure across the coil, and CO at the supply registers. Anyone who quotes you a repair from the doorway is guessing.
Need furnace repair in Brentwood, Franklin, or Spring Hill? Call (615) 254-6283 for same-day service.