Solar Panel Warranty: Product vs Performance Warranty Explained

A solar panel warranty consists of two separate commitments: the product warranty covers manufacturing defects in the panel, while the performance warranty covers the panel's power not falling below a certain curve over the years. For example, according to the datasheet, TommaTech's 605 W monofacial TOPCon model has a 15-year product warranty and a 30-year performance warranty. In this article we explain the difference between the two warranties, how to read a datasheet and what to look for in the warranty document for a system in Antalya.

Product warranty and performance warranty: the basic difference

The two concepts are often presented as a single "warranty", but their scopes are different.

• Product warranty: Covers material and workmanship defects. Faults arising from production, such as a glass breakage defect, frame, junction box or lamination problem, fall within this scope. The term varies by product.
• Performance warranty: Commits that the panel's output power will not fall below a certain percentage over time. This is a linear curve: a small drop in the first year, then a constant annual drop in later years.

Solar Nexo's website includes the phrase "the panel manufacturer's linear performance warranty of up to 30 years". This phrase means the panel manufacturer commits that the panel will stay above a certain power level for 30 years. It does not mean the whole system will run fault-free for 30 years; the inverter, battery and mounting elements are subject to separate warranty terms.

How do you read a solar panel warranty from the datasheet?

Read the warranty not from the sales brochure but from the manufacturer's datasheet and warranty document. The table below compares example values from manufacturer datasheets. These are product-specific examples; they cannot be generalized to all panels.

The important conclusion from the table is this: the phrase "30-year warranty" says nothing on its own. The power guaranteed in year 30 can be 87.4% or 84.95%. The product warranty can also be 12, 15 or 25 years; in other words, your right to claim for a defect in the panel varies by product. So when you see a claim of "25-year product warranty", ask which model it applies to; at TommaTech, 25 years appears only on the G2G double-glass version, while on the 144TN monofacial model it is 15 years.

A simple calculation: power guaranteed in year 30

If we apply the curve in the TommaTech datasheet to a 605 Wp panel: at least 99% in year 1, or about 599 W; at least 87.4% in year 30, or about 529 W. These figures are the guaranteed lower limit; real values often run above it. In field data, according to NREL's literature review, median degradation is around 0.5% per year; that study dates from 2012 and is not an upper limit for current TOPCon panels but only a point of comparison.

For a broader framework on panel lifespan and value loss over time, see our article on solar panel lifespan and value loss. Low annual degradation in TOPCon panels also affects the warranty curve; but this is a comparison of two models and should not be generalized to all products.

The inverter warranty is a separate matter

The inverter is the electronic heart of the system and its warranty is much shorter than the panel's. For example, on TommaTech on-grid and hybrid inverters the standard warranty is 5 years from the invoice date. Although this sits under the same roof as the panel's 30-year performance warranty, it requires a separate document and a separate service channel for the inverter. Extension options vary by brand; for this you need to look at the manufacturer's warranty document.

Because the panel's life is long, the inverter may need to be replaced once during the system's life. This is not a defect but a technical reality. Out-of-warranty repair and replacement costs should therefore be included in long-term planning. For inverter types and selection criteria, take a look at our article on inverters.

The battery warranty must be written by brand and model

With battery systems the warranty is even more complex. A battery warranty can be tied both to years and to energy throughput (or number of cycles). For example, the product warranty on TommaTech LV batteries is 60 months. LiFePO4 cycle life claims can differ greatly by product and source; conflicting figures are found in sources. For this reason, assess the battery warranty by brand and model, based on the written warranty document.

When choosing a battery, look not only at capacity but also at the warranty terms: how many years, up to what amount of energy, and under what temperature and discharge conditions. In Antalya's hot summers, the ventilation of the battery room bears directly on warranty conditions. For more information, see our article on LiFePO4 batteries.

Workmanship and installation warranty

The panel manufacturer does not guarantee the workmanship of the company that carries out the installation. The workmanship warranty is limited to the term and scope the installing company writes in the contract. Matters such as roof watertightness, cable connections, grounding and the mounting system fall within this warranty. You need to get the warranty term and scope in writing; a verbal commitment provides no assurance.

The manufacturer's datasheet also contains a warning: the panel must be mounted over a fire-resistant surface with sufficient ventilation behind it; it must not be installed on non-fire-resistant roofs such as plastic or PVC without a fire protection layer. Installation contrary to the installation manual voids the manufacturer's warranty. In other words, keeping the warranty depends on correct installation. On tile, sandwich panel or reinforced concrete roofs in Antalya, the mounting system should therefore be chosen according to the roof type.

What to check in the warranty document

1. Who gives the warranty? The panel manufacturer, the importer or the installer? Ask for a separate document for each.
2. Start date: The invoice date, the acceptance date or the production date?
3. Exclusions: Exclusions such as incorrect installation, natural disaster, lightning and misuse. For natural disaster and theft, see our article on solar panel insurance.
4. Service and contact: Whom and how to reach in the event of a fault; who bears shipping and removal-and-reinstallation costs.
5. Transferability: Whether the warranty passes to the new owner if you sell the house or facility.
6. Certificates and test reports: For the product's documents, see our article on solar panel certificates.

How is a warranty claim made?

The greatest help in a solar panel warranty claim is having orderly records. First document the fault or performance drop: the production graph from the monitoring system, the panel serial number, photos and, if any, a measurement report. Then apply in writing to the installing company and, if necessary, to the manufacturer's service channel.

In performance warranty claims, the panel's power is measured under standard test conditions; so an instantaneous drop in the field may not by itself be accepted as sufficient evidence. Soiling, shading, cable losses or an inverter problem also reduce production. In other words, a technician first needs to determine whether the problem is in the panel or in the system. This distinction both speeds up the warranty process and prevents unnecessary removals.

In Antalya, dust and pollen buildup is common in the summer months; such drops are mostly solved by cleaning and are not a warranty matter. Keeping a record that makes it easy to tell warranty from maintenance saves time in the solar panel warranty process.

The relationship between warranty and maintenance in Antalya

In Antalya, summer temperatures, salty air (in coastal areas) and dusty rain can affect the system's life. According to MGM (the Turkish State Meteorological Service), the average maximum temperature in July is 34.2 °C. The temperature coefficient of the panel is -0.30 %/°C for the TommaTech 144TN10, and power loss at high temperature is normal; this is not a defect but a physical property and is not counted as a fault under the warranty. Warranty and performance expectations should not be confused.

Regular maintenance and record keeping make a warranty claim easier. A user who tracks production data with a monitoring system can document a performance drop. Solar Nexo offers a "Maintenance and Technical Support" service after installation and, according to the information on its website, technical support runs 24/7. We can review the warranty documents together at the survey and project stage; you can reach us through our contact page.

Conclusion

When reading a solar panel warranty, ask three questions: how many years is the product warranty, what percentage of power is guaranteed in year 30, and what are the separate terms for the inverter and battery? The figures in the datasheet vary from model to model; the TommaTech 144TN10 has a 15-year product and 30-year performance warranty, and the G2G has a 25-year product warranty. Get all commitments in writing.

#Regulations and Applications#Warranty#Performance Warranty#Inverter Warranty#Datasheet