Somewhere around year eight, you will notice it. Your monitoring app shows production dipping — not dramatically, just a quiet slide. A few fewer kWh each month than last year, and a few fewer than the year before that. This is degradation, and every manufacturer on earth acknowledges it in their warranty documents. The question that matters is not whether your panels will lose output — they will — but how fast, what recourse you actually have when they underperform, and how much of the warranty's promise survives contact with the claims process.

The two types of solar panel warranty

Every solar panel ships with two separate warranties. They cover different things, last different durations, and trigger different claim processes. Confusing them — or letting a sales rep blur them into one reassuring phrase — is one of the most common mistakes homeowners make.

1. Product warranty (manufacturing defects)

This one is straightforward. The product warranty covers physical defects: cracked cells, failed junction boxes, corroded frames, delamination, electrical faults traceable to manufacturing. Panel breaks due to a defect? The manufacturer replaces it.

Product warranty durations by manufacturer: REC: 25 years. Qcells: 25 years. Canadian Solar: 12-15 years (enhanced warranty available at additional cost). LONGi: 15 years (recently extended to 25 on select models). Jinko Solar: 12-15 years. Trina Solar: 15 years. The gap between 12 and 25 years of product coverage is significant — a panel failure in year 14 is fully covered under a 25-year warranty and completely out of pocket under a 12-year warranty.

What is not covered: damage from external causes. Hail beyond the tested rating (typically 25mm at 23 m/s), falling debris, improper installation, rodent-chewed wiring. All of that falls to your homeowner's insurance, not the panel manufacturer. The product warranty protects you from the factory's mistakes, not from the world.

2. Performance warranty (output degradation)

The performance warranty is the one that addresses the slow fade. It guarantees the panel will produce at least a minimum percentage of its nameplate power rating over time — and its terms vary more than most homeowners realize.

Typical performance warranty terms: Year 1: guaranteed at 97-98% of nameplate. Years 2-25: linear degradation of 0.4-0.55% per year. Year 25: guaranteed at 84-87% of nameplate. For a 400W panel, this means guaranteed output of at least 340W (85%) at year 25. If the panel produces less than 340W at year 25, the manufacturer is obligated to repair, replace, or compensate.

Premium manufacturers tighten the guarantee considerably. REC Alpha Series guarantees 92% at year 25 — just 0.25% annual degradation. Standard-tier panels from Canadian Solar or Trina land at 84-84.8% at year 25 (0.5-0.55% annual degradation). The difference sounds academic until you do the math: on a 10 kW system over 25 years, the gap between 0.25% and 0.55% degradation amounts to approximately 750 kWh/yr by year 25, worth $135-$225 annually depending on your rate. Over the system's life, that adds up to real money.

What it actually takes to file a performance warranty claim

Here is where the warranty's practical value collides with reality. On paper, the manufacturer will act if a panel underperforms. In practice, proving that underperformance is your problem — and the process is neither simple nor cheap.

Red flag: To file a performance warranty claim, you typically need: (1) Independent performance testing of the specific panel, not the system — cost: $300-$600 for a professional system audit with panel-level IV curve tracing. (2) Production data from a monitoring system showing sustained underperformance relative to expected output. (3) Proof that site conditions (shading, soiling, inverter malfunction, wiring issues) are not causing the shortfall. If the manufacturer determines that a dirty panel, a new tree, or an inverter clipping issue caused the low output — not panel degradation — the claim is denied.

And even when a claim is approved, the remedy is usually a replacement panel — not cash. The manufacturer ships one (which may be a different model entirely, since yours was likely discontinued 15 years ago), but you pay for the labor to swap it. That labor cost runs $200-$500 per panel depending on roof access and system configuration. You won the claim and still wrote a check.

The practical reality: Most homeowners never file a performance warranty claim. The testing cost, the burden of proof, and the limited remedy make it economically marginal for a single underperforming panel. The performance warranty is most valuable if an entire batch of panels has a defect that causes accelerated degradation — a scenario that triggers class-action claims rather than individual warranty filings.

The inverter warranty gap

Panels get all the warranty attention in proposals, but they are only half the system. The inverter — the box that converts DC power from the panels to AC power for your home — often carries a warranty that expires a decade or more before the panels do.

  • String inverters (SolarEdge, Fronius, SMA): Typical warranty is 10-12 years. SolarEdge offers a 12-year standard warranty with an option to extend to 20 or 25 years at additional cost ($300-$600 for the extension). Fronius offers 10 years standard.
  • Microinverters (Enphase): 25-year warranty on IQ7 and IQ8 series. This is the only inverter technology that matches a 25-year panel warranty out of the box.
  • String inverter replacement cost: $1,500-$3,000 installed, depending on the model and labor rates. If your string inverter warranty expires at year 12 and your panels are warrantied for 25 years, you are covering 13 years of inverter risk out of pocket. Budget for at least one inverter replacement over the system's lifetime.
Red flag: A proposal that quotes "25-year warranty" without specifying which component has 25-year coverage is misleading. If the panels have a 25-year performance warranty but the string inverter has a 12-year warranty and the installer's workmanship warranty is 5 years, "25-year warranty" describes the longest warranty, not the coverage on every component. Ask for the warranty term on each: panels (product), panels (performance), inverter, and installer workmanship.

The workmanship warranty: the one that matters most early

In the first decade, the warranty you are most likely to need is not from a panel manufacturer or an inverter company. It is from the crew that bolted everything to your roof. The installer's workmanship warranty covers roof penetrations, flashing, wiring, racking, and electrical connections — and installation errors, not panel defects, cause the majority of early-life system problems.

Workmanship warranty durations: Budget installers: 2-5 years. Mid-range installers: 10 years. Premium installers (SunPower, Tesla in some markets): 25 years. The industry average is approximately 10 years. A roof leak caused by improperly sealed penetrations in year 6 is covered under a 10-year workmanship warranty but not under a 2-year warranty. Water damage remediation costs $2,000-$8,000 depending on severity.

And here is the uncomfortable part: the workmanship warranty carries the highest counterparty risk of any warranty in your system. Panel manufacturers are large, multinational corporations — they will almost certainly still exist in 2045. Your local installer? The residential solar industry has a brutal rate of turnover. Companies merge, go bankrupt, close up shop. If your installer disappears in year 4 of a 10-year workmanship warranty, the remaining six years of coverage vanish with them.

How to mitigate installer risk: Check the installer's years in business, state license status, and Better Business Bureau record. Ask whether the workmanship warranty is backed by a third-party insurance policy (some larger installers purchase warranty insurance that survives the company). If the installer is a subcontractor for a national brand (e.g., a local crew installing under the SunPower or Tesla banner), confirm whether the national brand or the local subcontractor backs the workmanship warranty.

What to verify on your proposal

  • Panel product warranty: Minimum 25 years from a Tier 1 manufacturer. Anything less than 15 years is a budget panel with higher long-term risk.
  • Panel performance warranty: 84% or higher guaranteed output at year 25. Look for the annual degradation rate — 0.5%/yr or less is standard; 0.25-0.3%/yr is premium.
  • Inverter warranty: 25 years for microinverters (Enphase). 12+ years for string inverters with the option to extend. If the proposal includes a 10-year string inverter warranty with no extension option, factor $2,000-$3,000 for replacement at year 10-12.
  • Installer workmanship warranty: 10 years minimum. Confirm whether it covers roof leak repair, electrical issues, and racking failure. Ask who backs the warranty if the company closes.

A warranty is a promise from a company that may or may not be around to keep it, enforced through a claims process that may or may not be worth the hassle. Read the actual warranty documents before signing — not the summary on the proposal, the full terms from the manufacturer. The summary always sounds better than the fine print.

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