Run capacitor
Common no-start and weak-compressor failure point. Match the microfarad and voltage rating.
Your furnace threw an error code, a technician is standing in your basement, and you have a quote for $800 in repairs. The furnace is 16 years old. Do you fix it or replace it?
This is the most expensive HVAC decision most homeowners make. Here is how to think through it correctly.
Jump to Fix
- The Age-and-Cost Rule
- 5 Signs You Should Replace, Not Repair
- What Repairs Actually Cost
- What a New Furnace Costs
- When Repair Makes Sense
The Age-and-Cost Rule
The industry standard calculation: if the repair cost exceeds 50% of the furnace’s remaining value, replace it.
A simpler version that works in practice:
| Furnace age | Repair quote | Decision |
|---|---|---|
| Under 10 years | Any amount | Repair — furnace has 10+ years left |
| 10–15 years | Under $500 | Repair if it has no other issues |
| 10–15 years | $500–$1,000 | Borderline — get a replacement quote first |
| 10–15 years | Over $1,000 | Replace |
| Over 15 years | Any repair over $400 | Replace — warranty is expired, efficiency has declined |
| Over 20 years | Anything | Replace — AFUE rating is likely 60–70% vs 95%+ on new units |
Annual efficiency cost: A 20-year-old 70% AFUE furnace costs roughly $430 more per year to run than a new 96% AFUE unit on a $1,500 annual gas bill. Factor that into any repair math.
5 Signs You Should Replace, Not Repair
1. Cracked Heat Exchanger
This is the non-negotiable replace signal. A cracked heat exchanger leaks combustion gases — including carbon monoxide — into your living space. There is no safe repair path. Replace the furnace.
2. The Repair Is the Blower Motor or Heat Exchanger
These are major components. A blower motor repair runs $400–$900. A heat exchanger runs $500–$1,500 for the part alone, plus 4–6 hours of labor. On a furnace over 12 years old, this money is better applied toward replacement.
3. You Have Called for Repairs Three Times in Two Years
Pattern failure means the system is aging out. Each repair buys you 12–18 months at best before the next component fails.
4. Your Gas Bill Increased Without Explanation
If your usage patterns haven’t changed but your bill went up 15–25%, efficiency has degraded. Dirty heat exchangers, failing inducer motors, and worn burners all reduce output. You are paying more for less heat.
5. Your Furnace Is More Than 25 Years Old
Modern 96% AFUE furnaces run circles around anything installed before 2000. A 25-year-old furnace may be operating at 60–70% AFUE. The payback on replacement via gas savings is typically 5–8 years.
What Repairs Actually Cost
Typical repair ranges from licensed HVAC contractors (parts + labor):
| Repair | Cost range |
|---|---|
| Igniter replacement | $150–$300 |
| Flame sensor cleaning or replacement | $80–$250 |
| Pressure switch replacement | $150–$350 |
| Inducer motor replacement | $400–$800 |
| Blower motor replacement | $400–$900 |
| Control board replacement | $350–$900 |
| Gas valve replacement | $350–$700 |
| Heat exchanger replacement | $800–$2,000 |
DIY note: Igniters and flame sensors are the two repairs most homeowners can do themselves with a screwdriver and a $15–$60 part from Amazon. If your error code points to one of these, check the DIY path before calling a tech.
What a New Furnace Costs
National average installed cost (2025–2026):
| Furnace type | Cost range | Notes |
|---|---|---|
| 80% AFUE single-stage | $2,200–$3,800 | Code minimum in many states. Lower upfront, higher operating cost |
| 96% AFUE two-stage | $3,200–$5,500 | Most popular choice. Best balance of upfront vs operating cost |
| 96%+ AFUE variable-speed | $4,500–$8,500 | Quietest, most efficient. Best for 2-story homes |
Brand factor: Carrier, Lennox, and Trane typically cost $500–$1,000 more than Rheem, Goodman, or York for equivalent efficiency tiers. Performance differences at the same AFUE are small. Installer quality matters more than brand.
Tax credit: The federal energy-efficient home improvement credit covers 30% of the cost of a qualifying heat pump furnace or high-efficiency gas furnace, up to $600 (gas) or $2,000 (heat pump). Check IRS Form 5695 for current limits.
When Repair Makes Sense
Repair is the right call when:
- The furnace is under 10 years old and the repair is a single component under $500
- The error code is an igniter, flame sensor, or pressure switch (all affordable DIY or low-cost service repairs)
- The furnace is 10–15 years old and the repair is under $300
- You are planning to sell the house in under 2 years and replacing isn’t justified by the timeline
Parts for Common DIY Repairs
If your error code points to a part you can swap yourself:
| Part | Fits most brands | Typical Amazon price |
|---|---|---|
| Universal hot surface igniter | Carrier, Goodman, Trane, Rheem | $15–$45 |
| Flame sensor (standard rod) | Most brands | $8–$25 |
| Pressure switch (brand-specific) | Match brand + model | $20–$60 |
Technician Tips
Make the repair-or-replace decision from the failure, age, efficiency, safety risk, and installed quote. A low-cost ignition or airflow repair often makes sense; a cracked heat exchanger, repeated lockouts, or expensive blower/control repairs on an old furnace often pushes toward replacement.
Parts note: Price the likely repair parts before deciding: igniter, flame sensor, pressure switch, limit switch, inducer motor, blower module, gas valve, and control board. Match every part to the model and serial number before comparing it with a replacement quote.
Need Replacement Parts?
Before ordering, match the furnace part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
For igniter replacement walkthrough, see: Best Furnace Igniter Replacement Guide
Get a Replacement Quote
If repair math points toward replacement, get at least two quotes from licensed contractors before committing. A second opinion on a $5,000 decision takes one phone call and can save $500–$1,500.
Typical quote timeline: most contractors can provide a same-day or next-day written quote for a standard single-family home installation.