Understanding your degradation curve
Why visualizing the curve helps
A chart makes the shape of degradation immediately intuitive in a way that a table of numbers or a single percentage doesn't, showing at a glance where the steepest drop happens and how gentle the decline becomes afterward. This is particularly useful for understanding why a panel's first year matters disproportionately compared to any single later year, since the curve visibly steps down more sharply right after installation. For a full production-based view across the same period, the 25 year output projection tool converts this curve into expected kWh.
What the shape of the curve tells you
The initial steeper drop reflects light-induced degradation, a one-time stabilization that happens as the panel is first exposed to sunlight, while the much gentler slope afterward reflects the steady, ongoing annual degradation rate that continues for the rest of the panel's working life. Comparing this shape against the annual output decline calculator's year-by-year table gives both the visual intuition and the precise numbers behind it. For a broader, plain-language introduction to owning solar, the Department of Energy's homeowner's guide to going solar is worth reading.
Why the warranty floor line matters
Manufacturers guarantee a minimum output percentage at year 25 as part of their performance warranty, and plotting that floor alongside your modeled curve shows the safety margin between expected typical performance and the worst-case guaranteed minimum. A modeled curve comfortably above the warranty floor suggests your panels are performing as expected, while a curve tracking close to or below that floor line would be worth investigating further using the warranty coverage value calculator. If financing is part of your decision, the loan APR impact calculator shows how the numbers play out over a comparable time horizon.
Using this curve alongside your real monitoring data
Once your system has been operating for a few years, compare your actual monitored output against this modeled curve at the corresponding year to see how closely reality tracks the expectation. Consistent tracking near or above the curve is a good sign, while output that falls noticeably and persistently below it across multiple years is worth a closer look using the panel lifespan estimator or a professional inspection. For a broader, plain-language introduction to owning and maintaining solar, the Department of Energy's guide to operating and maintaining a PV system is a good starting point.