Estimate wall insulation returns with cashflow, NPV, and payback. Compare rebates, financing, and escalation quickly. See savings trends yearly, then export reports instantly securely.
| Scenario | Area | Installed cost | Energy cost | Savings rate | Estimated payback |
|---|---|---|---|---|---|
| Conservative | 120 m² | 1,560 | 1,800/yr | 12% | ~8–10 yrs |
| Balanced | 140 m² | 1,960 | 2,000/yr | 18% | ~5–7 yrs |
| Optimistic | 160 m² | 2,240 | 2,600/yr | 25% | ~3–5 yrs |
Start with an accurate annual heating and cooling bill. Many households enter 1,200 to 3,000 per year, then test savings rates from 10% to 30%. A 2,000 baseline at 18% yields 360 in first‑year gross savings before maintenance or financing.
Climate factors can shift results materially. In colder regions, a 1.2 multiplier can lift the 360 saving to 432, while mild zones may reduce it to 288. Use realistic occupancy assumptions and confirm insulation thickness and target R‑value with your installer to avoid overstating benefits during peak seasons.
Total project cost equals insulated wall area times installed cost per unit. Typical inputs range from 8 to 25 per square meter, depending on material and access. For 140 m² at 14, the installed cost is 1,960. Apply rebates up front and optionally place a tax credit in year one.
The calculator escalates energy prices to reflect utility inflation. With 4% escalation, the second‑year gross savings becomes 374. If annual maintenance is 30, net savings become 344. Cumulative cashflow compares these savings against the initial outlay to estimate payback, often between 3 and 10 years. For example, if installed cost is 1,960 and year‑1 net cashflow is 340, five‑year cumulative reaches about 1,820, leaving a small remaining balance for payback.
NPV discounts future cashflows using your required return, commonly 6% to 10%. Positive NPV suggests the project beats that hurdle. IRR estimates the break‑even discount rate. Shorter lifespans reduce NPV quickly, while higher escalation improves NPV. Use the sensitivity fields to stress‑test conservative and optimistic scenarios.
Compare multiple scenarios by adjusting savings rate, climate factor, and financing term. The chart highlights whether early loan payments delay payback. Export CSV for audit trails and shareable budgets, and generate a PDF summary for contractors or lenders. When final quotes arrive, rerun inputs to lock a decision.
If you are unsure, test 10%, 18%, and 25%. Choose the most conservative rate that matches your home’s leakage level, insulation type, and climate.
Payback is the first year when cumulative net cashflow becomes positive. The calculator also estimates a fractional year by interpolating between the last negative and first positive cumulative values.
Yes. Rebates reduce the upfront cost immediately. Credits are treated as a year‑one cash inflow, which improves payback, ROI, and NPV, especially for smaller projects.
Use a rate that reflects your alternatives and risk, often 6%–10%. A higher discount rate makes future savings less valuable and lowers NPV.
Financing can delay payback because loan payments reduce early net cashflow. However, if the project is cash‑constrained, financing may still be attractive when NPV remains positive.
No. The outputs focus on energy cashflows only. Better comfort, reduced drafts, and potential resale benefits can be meaningful, so consider them as additional upside beyond the ROI shown.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.