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HVAC & Climate Control

Furnace AFUE Upgrade Savings Calculator

Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE).

Estimate gas savings when upgrading furnace efficiency (AFUE). Planning estimates only — verify measurements and local codes on site.

Inputs

6095
8098
503000
0.55
025000

Smart analysis

Recommendations

Tailored to your live inputs and result—guidance only, not professional advice.

  • Interpret

    Treat this as a planning estimate

    Primary result: Annual gas savings = $142.11. Re-run with optimistic and pessimistic inputs to understand the range—not just a single point.

Scenario studio

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Scenario A

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Scenario B

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Plain-English guide

Terms & how it works

Confused by a field? Read the short definitions here while you use the tool.

  • Old AFUE (%)

    The “Old AFUE (%)” value used in this tool’s formula. Adjust it to see results update live.

  • New AFUE (%)

    The “New AFUE (%)” value used in this tool’s formula. Adjust it to see results update live.

  • Annual gas therms

    The “Annual gas therms” value used in this tool’s formula. Adjust it to see results update live.

  • Gas rate ($/therm)

    The “Gas rate ($/therm)” value used in this tool’s formula. Adjust it to see results update live.

  • Upgrade cost

    One-time or recurring costs that affect total money paid.

  • upgradeCost

    Upgrade cost ($)

    The “Upgrade cost ($)” field. Default 4500; typical range 0–25000.

How this calculator works

Estimate gas savings when upgrading furnace efficiency (AFUE). Planning estimates only — verify measurements and local codes on site. Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE). Example: 600 therms at 80% AFUE → 95% AFUE saves ~95 therms/year.

Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE).

Example: 600 therms at 80% AFUE → 95% AFUE saves ~95 therms/year.

When to use this Furnace AFUE Savings

Common use cases

  • Estimate gas savings when upgrading furnace efficiency (AFUE).
  • Sanity-check with this case: 600 therms at 80% AFUE → 95% AFUE saves ~95 therms/year.
  • The relationship is: Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE).

Localized examples

  • HVAC & Climate Control: the example on this page uses the same formula as the widget.

What you get

  • Fields: Old AFUE (%), New AFUE (%), Annual gas therms, Gas rate ($/therm)
  • Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE).
  • Example on the page: 600 therms at 80% AFUE → 95% AFUE saves ~95 therms/year.

How to Calculate Furnace AFUE Savings Step-by-Step

  1. 1Enter Old AFUE (%), New AFUE (%), Annual gas therms, then the remaining fields. Use the values you have, not a catalog average, unless that is all you know.
  2. 2Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE).
  3. 3Worked case: 600 therms at 80% AFUE → 95% AFUE saves ~95 therms/year.
  4. 4Buy materials after you walk the job. This is a first-pass quantity, not a purchase order.

Governing formula

Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE).

600 therms at 80% AFUE → 95% AFUE saves ~95 therms/year.

Example: set Old AFUE (%) = 80, New AFUE (%) = 95, Annual gas therms = 600, then read the result.

Variable definitions

  • oldAfue

    Old AFUE (%)

    The “Old AFUE (%)” field. Default 80; typical range 60–95.

  • newAfue

    New AFUE (%)

    The “New AFUE (%)” field. Default 95; typical range 80–98.

  • annualTherms

    Annual gas therms

    The “Annual gas therms” field. Default 600; typical range 50–3000.

  • gasRate

    Gas rate ($/therm)

    The “Gas rate ($/therm)” field. Default 1.5; typical range 0.5–5.

  • upgradeCost

    Upgrade cost ($)

    The “Upgrade cost ($)” field. Default 4500; typical range 0–25000.

  • The takeoff (Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE).) ignores waste, code, and what you find when you open the wall. Measure twice on site.
  • Nothing here is uploaded for the calculation itself.

Frequently Asked Questions

Useful heat fixed; new therms = old therms × (old AFUE ÷ new AFUE).

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Reviews & Ratings

See what others think about this tool, then leave your own rating to help improve CalculioHub.

4.8

out of 5.0

4 reviews

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Your rating

Aisha K.

Mar 12, 2026

Clean layout and the results update instantly. Exactly what I needed for a quick planning check.

Daniel R.

Feb 28, 2026

Very usable on mobile. Would love a save/export option later, but the math feels solid.

Priya S.

Feb 3, 2026

The FAQ section answered my questions before I even had to search. Smooth dark mode too.

Marcus L.

Jan 19, 2026

Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.

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