{
  "slug": "panel-degradation-25yr",
  "title": "Solar Panel Degradation Over 25 Years Calculator",
  "heading": "Solar Panel Degradation Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/panel-degradation-25yr",
  "summary": "Project your system's output decline over its warranty life.",
  "description": "Solar panels don't produce the same output forever — silicon degrades slowly from UV exposure, thermal cycling, and micro-cracking, typically 0.3-0.8% per year depending on panel quality and manufacturer. Most warranties guarantee 90-92% of original output at year 10 and 80-85% at year 25. This calculator projects year-by-year output decline from a chosen first-year production and degradation rate, and checks whether your production stays above your manufacturer's warranty floor across the panel's life — useful for verifying a quote's long-term production claims or estimating output on an existing system you're evaluating for a home purchase.",
  "formula": "Year N output = year 1 output × (1 − degradation rate)^(N−1).",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=panel-degradation-25yr",
  "inputs": [
    {
      "id": "year1Production",
      "label": "Year 1 annual production",
      "kind": "number",
      "hint": null,
      "default": 12000,
      "unit": "kWh",
      "min": 500,
      "max": null
    },
    {
      "id": "degradationRate",
      "label": "Annual degradation rate",
      "kind": "number",
      "hint": null,
      "default": 0.5,
      "unit": "%",
      "min": 0.1,
      "max": 1.5
    },
    {
      "id": "warrantyYear",
      "label": "Check output at year",
      "kind": "number",
      "hint": null,
      "default": 25,
      "unit": null,
      "min": 1,
      "max": 30
    },
    {
      "id": "warrantyFloorPct",
      "label": "Manufacturer warranty floor at that year",
      "kind": "number",
      "hint": null,
      "default": 85,
      "unit": "%",
      "min": 50,
      "max": 100
    }
  ],
  "outputs": [
    {
      "id": "outputAtYear",
      "label": "Projected production at chosen year",
      "format": "number",
      "hint": null,
      "primary": true
    },
    {
      "id": "pctOfOriginal",
      "label": "Percent of original output remaining",
      "format": "percent",
      "hint": null,
      "primary": false
    },
    {
      "id": "meetsWarranty",
      "label": "Meets warranty floor? (1=yes)",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "lifetimeTotal",
      "label": "Cumulative production through that year",
      "format": "number",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Year 1 annual production: 12000 kWh",
      "Annual degradation rate: 0.5 %",
      "Check output at year: 25",
      "Manufacturer warranty floor at that year: 85 %"
    ],
    "outputs": [
      "Projected production at chosen year: 10,640",
      "Percent of original output remaining: 88.7%",
      "Meets warranty floor? (1=yes): 1",
      "Cumulative production through that year: 282,671"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter year 1 annual production (kWh).",
      "Enter annual degradation rate (%).",
      "Enter check output at year.",
      "Enter manufacturer warranty floor at that year (%).",
      "Read your projected production at chosen year on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "year1Production": 7200,
        "degradationRate": 0.3,
        "warrantyYear": 15,
        "warrantyFloorPct": 51
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "year1Production": 12000,
        "degradationRate": 0.5,
        "warrantyYear": 25,
        "warrantyFloorPct": 85
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "year1Production": 19200,
        "degradationRate": 0.8,
        "warrantyYear": 30,
        "warrantyFloorPct": 100
      }
    }
  ],
  "limitations": [
    "Estimates assume standard, average conditions — local rules, pricing, and materials vary.",
    "Results are rounded for readability; add a buffer before ordering, booking, or committing.",
    "Double-check anything with a real cost attached against a local quote."
  ],
  "faq": [
    {
      "q": "What degradation rate should I actually expect?",
      "a": "Tier-1 monocrystalline panels from major manufacturers (REC, Qcells, Panasonic, LG while it existed) typically run 0.3-0.5% annual degradation; budget or older polycrystalline panels can run 0.7-1%+. NREL field studies of real installed systems found a median around 0.5-0.6% annually across a wide range of panel ages and types."
    },
    {
      "q": "How is the warranty floor different from the degradation rate?",
      "a": "The warranty floor (e.g., '85% of original output guaranteed at year 25') is a legal minimum the manufacturer will replace or credit panels for if not met; the actual degradation rate that panels experience in the field is usually better than the conservative number baked into the warranty terms, so most systems outperform their warranty floor throughout their life."
    },
    {
      "q": "Does degradation happen at a steady rate every year?",
      "a": "Not quite — many panels show a slightly higher 'initial light-induced degradation' (LID) of 1-3% in the first few months of exposure, then settle into the steady linear annual rate this calculator models. Some newer panel technologies (PERC, TOPCon) have reduced this initial LID step significantly."
    },
    {
      "q": "Should I worry about a system's output at year 25?",
      "a": "Not usually cause for alarm — even at 85% of original output, a well-sized system installed for 100% offset in year 1 is still covering roughly 85% of your usage 25 years later, and most panels continue producing usable power well past their 25-year warranty period, just below the guaranteed floor."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/solar-array-sizing",
    "https://www.revenuelab.fyi/toolbox/solar-payback-itc",
    "https://www.revenuelab.fyi/toolbox/roof-orientation-derate"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Solar Panel Degradation Over 25 Years Calculator (https://www.revenuelab.fyi/toolbox/panel-degradation-25yr)"
}