Should You Repair or Replace Your Furnace?
Use the $5,000 rule to find out whether it makes more financial sense to repair your current furnace or invest in a replacement.
Should You Repair or Replace Your Furnace?
Enter your furnace details below for a recommendation.
How the $5,000 Rule Works
The $5,000 rule is a widely-used guideline in the HVAC industry for deciding whether to repair or replace a furnace. The formula is simple:
Furnace Age (years) × Repair Cost ($) = Rule Score
If the score exceeds $5,000, replacement is the better investment.
This rule accounts for the fact that older furnaces are more likely to need additional repairs soon, and their remaining useful life may not justify a costly fix. A newer furnace with the same repair cost scores lower, making repair more worthwhile.
Frequently Asked Questions
What is the $5,000 rule for furnaces?
The $5,000 rule is a simple formula: multiply your furnace's age (in years) by the estimated repair cost. If the result exceeds $5,000, it's generally more cost-effective to replace the furnace rather than repair it. For example, a 15-year-old furnace needing a $400 repair scores $6,000 — suggesting replacement.
How long does a furnace typically last?
A well-maintained furnace typically lasts 15 to 20 years. Some high-quality units can last up to 25 years. If your furnace is approaching or past 15 years, factor its remaining lifespan into your repair-vs-replace decision.
How much does a new furnace cost?
A new furnace (including installation) typically costs $3,500 to $7,500 for a standard-efficiency unit, or $5,000 to $10,000 for a high-efficiency model. Costs vary by region — expect to pay more in states with higher costs of living.
What does AFUE mean?
AFUE (Annual Fuel Utilization Efficiency) measures how efficiently your furnace converts fuel to heat. An 80% AFUE furnace converts 80% of fuel to heat, losing 20% to exhaust. High-efficiency furnaces rated 95%+ waste very little fuel and can save hundreds per year on heating bills.
When should I definitely replace my furnace?
Consider replacing your furnace if: it's over 15 years old and needs a major repair (heat exchanger, blower motor), your heating bills have been increasing steadily, it requires frequent repairs (2+ per season), or it has a cracked heat exchanger (a safety hazard).
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