Calculator
Enter baseline costs, expected savings, incentives, and advanced assumptions. Then calculate to view ROI metrics and cash flows.
Example data table
A sample scenario to illustrate inputs and estimated outputs.
| Sample inputs | Value | Estimated outputs |
|---|---|---|
| Device + install | $309.00 | Net initial outflow |
| Rebate | $60.00 | $249.00 |
| Heating & cooling spend | $950.00 + $650.00 | First-year savings |
| Heating & cooling savings | 9% + 11% | $157.00 |
| Escalation / discount / years | 3% / 6% / 10 | Payback / ROI / NPV |
| — | — | 1.57 yrs / 622.82% / $1,057.05 |
Formula used
- Annual gross savings = (HeatingSpend × HeatingSavings%) + (CoolingSpend × CoolingSavings%).
- Escalation: each year’s baseline and savings grow by (1 + Escalation%)^(Year−1).
- Year 1 adjustment: savings are reduced by the average monthly factor from Delay and Ramp-up.
- Net cash flow (year y) = GrossSavings − (Maintenance + FinancingPayments + ReplacementCost).
- NPV = Σ CashFlow_t / (1 + DiscountRate)^t, including year 0 outflow.
- Payback: the first point where cumulative cash flow becomes positive (linear interpolation within that year).
- ROI% = (TotalNetBenefit ÷ TotalCosts) × 100.
- IRR is the rate where NPV equals zero (iterative estimate).
How to use this calculator
- Enter your annual heating and cooling costs from recent bills.
- Set savings percentages based on your expected behavior changes.
- Add rebates or credits to reduce the device purchase cost.
- Choose an analysis window and discount rate for time value.
- Optional: enable advanced options for delays, ramp-up, or financing.
- Click Calculate ROI to see results above the form.
- Use the download buttons to export the report as CSV or PDF.
Baseline spend drives savings accuracy
Choosing financed mode spreads device payments across the loan term while keeping installation upfront. Financing can delay payback if payments exceed early savings, but it may improve affordability when cash on hand is limited. Use scenarios to compare comfort gains against quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly simply directly today quickly carefully consistently realistically practically confidently clearly costs. now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now now
FAQs
What savings percentages should I use?
Start with 5–15% for heating and 5–20% for cooling, then adjust using past behavior. Conservative inputs reduce the chance of overstating ROI, especially in mild climates.
How does energy price escalation affect results?
Escalation increases future baseline costs and therefore future savings. Higher escalation improves long‑term totals, but NPV still depends on your discount rate and the timing of cash flows.
Why can ROI be positive but NPV negative?
ROI uses nominal totals, while NPV discounts future benefits. If most savings arrive later, a higher discount rate can push NPV below zero even when total savings exceed costs.
What if I finance the thermostat?
Financing spreads device payments across months, changing early-year net cash flow. Payback may lengthen if payments exceed initial savings, but total savings potential remains similar.
Should I include replacement cost?
If you expect a replacement within your analysis window, include it to avoid overstating returns. Set replacement year to 0 to disable if you are modeling only the first device.
How should I interpret IRR?
IRR is the annualized rate where discounted value equals zero. Use it to compare investments, but treat it cautiously when cash flows change direction multiple times or when results show N/A.