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    Solar Panel Warranties Explained: Panels, Inverters, Workmanship & Degradation

    Understanding the four types of solar warranty helps you compare quotes properly and avoid costly surprises.

    The Four Warranties You Should Check

    Product Warranty (Panels)

    Manufacturing defects, delamination, junction box failure, glass breakage (not weather damage)

    Typical
    12–25 years
    Premium
    25–30 years
    Watch For
    Some manufacturers offer 10-year product warranties as standard — look for 25+ years from Tier 1 brands.

    Performance / Degradation Guarantee

    Guarantees minimum power output over time. If panels degrade faster than specified, manufacturer replaces or compensates.

    Typical
    25 years (≥80% output)
    Premium
    30 years (≥87% output)
    Watch For
    Check the degradation curve — linear guarantees (e.g., 0.4%/year) are better than stepped guarantees (e.g., 90% at year 10, 80% at year 25).

    Inverter Warranty

    Component failure, firmware issues, performance below spec. Inverters are the most likely component to need replacement.

    Typical
    5–12 years
    Premium
    20–25 years (micro/optimisers)
    Watch For
    String inverters typically offer 5 years standard (extendable to 10–20). Microinverters often include 20–25 year warranties as standard.

    Workmanship / Installation Warranty

    Roof leaks from mounting, wiring faults, incorrect installation, scaffolding damage. Provided by your installer, not the manufacturer.

    Typical
    2–10 years
    Premium
    10–20 years
    Watch For
    This is the most variable warranty. Insist on minimum 10 years. Check if it's insurance-backed (survives if installer ceases trading).

    Understanding Degradation Rates

    What's Normal?

    • Year 1: ~2% initial degradation (light-induced)
    • Years 2–25: 0.25–0.5% per year (standard panels)
    • After 25 years: typically still producing 80–87% of original output
    • Premium panels (HJT, N-type): 0.25% or less per year

    Linear vs Stepped Guarantees

    Linear: Guarantees a maximum degradation rate per year (e.g., 0.4%/year for 25 years = ≥90% at year 25). This is the better standard.

    Stepped: Only guarantees output at specific milestones (e.g., 90% at year 10, 80% at year 25). Less protective — allows faster degradation in early years.

    Making a Warranty Claim

    Keep These Documents

    • • MCS installation certificate
    • • Panel serial numbers and datasheets
    • • Inverter serial number and warranty card
    • • Installer workmanship warranty document
    • • Original quote and specification
    • • Monitoring data (generation history)

    What If the Installer Goes Bust?

    • Product warranties are with the manufacturer — unaffected
    • Workmanship warranties — only protected if insurance-backed
    • RECC/HIES membership provides insurance-backed guarantees
    • Always check if workmanship warranty is insurance-backed before signing

    Related Guides

    Best solar panels for UK homes →Solar inverter options →

    Compare Warranties Across Quotes

    Our quotes include full warranty breakdowns — panels, inverter, and workmanship — so you can compare like for like.

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