Repair or Replace? How to Know When Your Furnace is Dead Money

Stop paying for endless repairs. Learn when investing in a new system is actually the cheaper option.

January 8, 2026 HVAC Buying Guide

It's the question every homeowner dreads when their furnace breaks down: "Do I pay $600 to fix this old thing, or do I bite the bullet and buy a new one?"

Making the wrong choice can be expensive. Fix it, and it might break again next week. Replace it too early, and you lose value. Here is the professional criteria we use to help clients decide.


1. The 50% Rule

This is the golden rule of HVAC. If the cost of the repair is 50% or more of the cost of a new system, you should replace it. It simply doesn't make financial sense to invest that much capital into a depreciating asset.

2. The Age Factor (15+ Years)

The average life expectancy of a furnace in Michigan is 15 to 20 years. If your unit is over 15 years old and needs a major repair (like a blower motor or heat exchanger), it is living on borrowed time. Parts are harder to find, and efficiency has likely dropped significantly.

Technician inspecting an older furnace in a Detroit home basement

3. Your Energy Bills Are Skyrocketing

Have you noticed your gas bill creeping up, even though you haven't changed your thermostat habits? As furnaces age, they lose efficiency. A modern high-efficiency furnace can operate at 96% efficiency or higher. Upgrading could save you 20-30% on your monthly heating costs, which helps the new system pay for itself over time.

Get an Honest Opinion

We aren't here to push a sale if you don't need one. But we also don't want you wasting money on a "money pit" furnace.

Unsure what to do? Contact Mechanical Temp for a free estimate . We'll give you the numbers so you can make the smart choice for your wallet and your warmth.