Insulation energy savings & payback calculator
Will more insulation pay for itself? This gives a rough, relative answer from your own heating bill: how much less heat escapes an assembly after you add R, and how many years the savings take to cover the cost. It is a sanity check, not an audit.
Calculator
Going from R-11 to R-38 cuts heat loss through that assembly about 71.1%; on $1,200.00/yr heating with 25% through it, that is roughly $213.16/yr — a 7.0-year simple payback. A ROUGH RELATIVE estimate from YOUR own heating bill — NOT an energy audit, HVAC sizing or a guaranteed saving.
Formula
reduction = 1 − (U_after ÷ U_before) · savings = heating_cost × share × reduction · payback = cost ÷ savings
With U = 1 ÷ R, the fractional cut in heat loss through an assembly is 1 − U_after/U_before — a clean, relative number. It is applied only to the share of your bill that actually leaves through that surface.
Worked example
Take a wall from R-11 to R-38. U goes from 1÷11 = 0.0909 to 1÷38 = 0.0263, a heat-loss cut of 1 − 0.0263/0.0909 = 71.1% through that wall. If you spend $1,200/year on heat and about 25% of your loss goes through it, that is 1,200 × 0.25 × 0.711 = about $213/year. A $1,500 job then pays back in 1,500 ÷ 213 = about 7.0 years. Rough, and only as good as your 25% guess — but enough to know whether it is worth pricing.
What this does and does not tell you
This is deliberately a relative estimate. Read it with its limits in mind:
- It is not an energy audit or HVAC sizing. There is no climate model, no BTU load, no equipment. It compares heat loss through one assembly before and after — nothing more. For a real assessment, hire a certified energy auditor.
- The "share" input is the soft spot. How much of your bill leaves through this attic or wall is a guess. Attics are often the biggest single share; walls and floors less. Try a range (say 15%–35%) and see how the payback moves.
- Diminishing returns are real. Going from R-0 to R-13 saves far more than R-30 to R-49. The tool shows this: the first inches always cut the most loss, so do not over-insulate a wall that is already decent when an uninsulated one is begging for it.
- Air-sealing often beats R. A leaky house loses heat by air movement, not just conduction — sealing gaps can pay back faster than the next batt. This model does not capture that, so treat air-sealing as a separate, usually cheaper, win.
No guaranteed-savings claim: actual savings depend on air-sealing, climate, the whole envelope and your fuel price. Use it to rank upgrades, then price the winner with the installation cost tool.
Reference table
| Before | After | U before → after | Heat-loss cut |
|---|---|---|---|
| bare (R-0) | R-11 | ∞ → 0.0909 | 100% |
| R-11 | R-38 | 0.0909 → 0.0263 | 71% |
| R-19 | R-49 | 0.0526 → 0.0204 | 61% |
| R-11 | R-49 | 0.0909 → 0.0204 | 78% |
| R-30 | R-60 | 0.0333 → 0.0167 | 50% |
The reduction is per assembly, not for the whole house — a wall going from R-11 to R-38 cuts that wall’s loss ~71%, but it is only part of your bill. A relative estimate, not an energy audit.
Frequently asked questions
How much will adding insulation save me?
It depends on how leaky the assembly is now and how much of your bill escapes through it. Taking a wall from R-11 to R-38 cuts that wall’s loss ~71%; on a $1,200 bill with 25% going through it, that is roughly $213/year. Your numbers will differ — it is a rough, relative estimate.
What is a good payback for insulation?
Attic insulation often pays back in a handful of years because attics lose so much heat; deep wall retrofits take longer. Anything under ~10 years is generally attractive, but the real driver is how bad the assembly is now.
Is this an energy audit?
No. It is a relative heat-loss comparison from your own bill, not an audit, HVAC sizing or a guaranteed saving. For a certified assessment, hire a licensed energy auditor.
Should I air-seal or add insulation first?
Usually air-seal first — stopping air leaks is often cheaper and pays back faster than the next layer of R, and it makes the insulation you add work as rated. This tool models conduction only, so it does not credit sealing.