Energy Savings ROI Calculator

Instead of dividing net cost by a flat monthly savings figure, the calculator steps through the upgrade's lifespan month by month, compounding your entered Annual Utility Rate Increase onto the monthly savings amount at the start of each new year. It accumulates these growing monthly savings until they cross your net cost after rebate, and reports that crossover point in months — so a higher rate increase produces a shorter payback period than a naive flat calculation would.

The 10-year projection always runs for exactly 10 years regardless of what you enter for lifespan, applying the same compounding utility-rate-increase logic used in the payback calculation. This gives you a standardized comparison point across different upgrades even if their expected lifespans differ, though it means the figure can extend savings beyond an upgrade's actual expected life if lifespan is under 10 years.

It's (10-year total savings minus net cost after rebate) divided by net cost after rebate, expressed as a percentage — essentially your net return over the initial investment across that 10-year window. It returns 0% if your net cost after rebate is zero or negative, since ROI as a ratio to cost is undefined in that case.

No — it only compounds the utility rate increase onto your entered monthly savings; it assumes the upgrade's own performance (like solar panel output or insulation effectiveness) stays constant across its lifespan. Real equipment often degrades somewhat, so actual long-run payback could run longer than what's shown here.