BoilerComparison2026-02-20
Condensing vs Non-Condensing Boilers
Condensing boilers recover flue heat for 90%+ efficiency; non-condensing units waste it.
If your boiler is more than 15 years old, it's likely non-condensing. Here's why condensing is the modern standard.
How condensing works
Condensing boilers extract extra heat from flue gases, reaching 90–95%+ AFUE versus 60–80% for old non-condensing units — a major cut in gas use.
What it means for you
Upgrading to condensing lowers bills and qualifies for rebates, but requires a condensate drain and modern venting.
Key takeaways
- Condensing: 90%+ AFUE, lower bills
- Non-condensing: 60–80%, outdated
- Condensing needs a condensate drain
- Most rebates require condensing units
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