25-Year Savings Projector: the whole-life truth about a solar system

What this calculator is

The Savings Projector is the long-view companion to the Payback Calculator. Instead of a single break-even date, it builds the system’s entire 25-year cash story: production that fades 0.5% a year, electricity prices that climb at your chosen rate, the split between power you consume yourself (worth full retail) and power you export (worth whatever your utility actually pays), yearly upkeep, and a mid-life inverter replacement. The chart shows your cumulative position crossing zero — your true break-even — and where it ends.

How it works

Each year the tool values your production in two parts. Self-consumed electricity avoids a purchase at the full retail rate. Exported electricity earns your export percentage of that rate — 100% under classic net metering, often 20–40% under net billing, near zero where exports are compensated at wholesale avoided cost. Prices escalate yearly; production degrades yearly; upkeep and the year-13 inverter swap are subtracted as they occur.

Worked example (real numbers)

Limitations

• Policy can change mid-life. Export rules have been revised repeatedly (Nevada 2015, California 2023). Existing systems are often grandfathered for a period, but no projector can insure against rule changes.
• Self-consumption is estimated, not metered. Real self-use depends on when your household runs loads. Daytime-heavy homes self-consume 60–80%; empty-by-day homes may manage 30–40% without a battery.
• No discounting. Totals are nominal dollars, not inflation-adjusted net present value. A dollar saved in year 24 is counted like a dollar in year 1 — fine for comparison, generous in absolute terms.
• Roof and removal costs excluded. Add your own figures to net cost if a re-roof or panel removal is likely during the 25 years.

Common mistakes

• Projecting with 100% export credit by default. Most new US systems no longer get it. Find your tariff first — our net metering guide shows how to read it.
• Ignoring degradation and the inverter. Brochure projections that hold year-1 savings flat for 25 years overstate totals by 15–25%.
• Counting savings on power you’d export at midday in summer at full retail while your plan pays avoided-cost. The two-part valuation above exists precisely to stop this.
• Forgetting the fixed charge. Your connection fee stays on every bill forever; “savings” here correctly exclude it because production can’t offset it.

Questions about long-term savings

Why include an inverter replacement?

String inverters typically last 10–15 years against 25-year panels. Budgeting ≈$2,400 around year 13 is the honest mid-life cost that most “25-year savings” claims quietly omit. Microinverters often carry 25-year warranties instead — adjust the cost input via net cost if your quote includes them.

Does a battery raise projected savings?

Under net billing, yes: storing midday surplus for evening use converts low-value exports into full-retail self-supply. Under full net metering, a battery adds little financially — its value there is backup power. Model it by raising self-use toward 85–90% and adding the battery price to net cost.

What escalation rate should I use?

3% matches the long-run US residential trend. Coastal and high-demand states have run hotter (4–6% in recent years); regulated low-cost states cooler. Always sanity-check your result at 0% — if the system only works at 5% escalation, it doesn’t work.

Rates, prices and incentive rules on this page checked November 2026.

Disclaimer: planning estimates only — not financial advice, not a guarantee of future prices, production or policy. Electricity tariffs and incentive rules change; verify current terms with your utility and state energy office.