30-Year Linear Power Warranty: What Buyers Should Verify

Published: October 20, 2026 | Author: Weltrus Energy Team | Reading Time: 12 minutes

When the Brochure Says 30 Years

Procurement teams see the same phrase on quotations, datasheets, and slide decks: 30-year linear power warranty. Two suppliers can print that phrase and still promise different watts in year 30. One may mean a performance schedule. Another may be pointing at a product term, a type-test report, or a sentence that never appears in the limited warranty PDF.

The buyer pain shows up after commissioning, not at bid opening. A lender asks which legal entity pays if power falls short. An EPC asks whether the clock started at the factory gate or at commercial operation. A later owner asks whether the warranty moved with the project company. None of those answers sit in the phrase “30-year linear.”

Treat the phrase as a label that must resolve to four facts: the warranted percentage of nameplate at each year, the test used to measure it, the legal entity that stands behind it, and the remedy if the module fails the test. If any of the four is missing, the line is a marketing statement. It is not yet a buying specification.

Power Warranty, Product Warranty, and the Certificate

A module shipment is usually covered by two warranty texts, often inside one limited-warranty PDF, plus a separate qualification file. They answer different questions. Mixing them is how a short product term gets described as a 30-year promise.

Read the product term as its own number. Some limited warranties cover workmanship for 12 years, some for 15, some for 25, and the power schedule runs longer. After the product term ends, a cracked backsheet, a failed diode, or a loose junction box may sit outside the workmanship clause even when output is low. Whether that failure still qualifies as a power claim depends on the wording of defects, normal application, and exclusions. Quote the clause. Do not infer it from the longer year count.

The warrantor is the legal name in the warranty, not the logo on the pallet. The contract party, the factory, and the warrantor can be three names. If a parent company is the real backstop, the file needs that guarantee, with a name and an address, not a sentence in an email. Territory matters the same way. A warranty drafted for one sales region may exclude the country where the array will be installed. Transfer matters when the project company will be sold: the text either allows assignment to a later owner or it does not.

The start date is a defined event. Common choices are the ship date, the delivery date, the installation date, or commercial operation. A plant commissioned 18 months after shipment has already consumed 18 months if the clock starts at the factory. Write the event into the purchase order so the packing-list date and the warranty date describe the same moment.

How to Calculate the Linear Floor

Linear describes the guaranteed floor. It means the minimum allowed power steps down by a stated amount each year after the first-year allowance. It does not mean a module on a roof loses exactly that percentage in every calendar year. Field loss depends on climate, soiling, shade, and how the array is built. The warranty is the floor you can claim against, measured the way the warranty specifies.

On the Weltrus parameter tables for the 465–490 W, 540–560 W, and 645–670 W three-piece TOPCon lines, the degradation line is printed as first year ≤1.0% and linear 0.35% per year. The same internal sheet points to IEC 61215, IEC 61730, and TUV SUD as qualification evidence. Those standards are type tests. They are not a 30-year outdoor measurement. Use the printed rates as the schedule to check, and bind the purchase to the limited warranty for that model and revision.

Read the 1.0% as a first-year cap on loss from nameplate, so the end of year 1 is at least 99.0% of nameplate. Read the 0.35% as one step for each later year. From year 2 through year 30 there are 29 steps. Twenty-nine times 0.35% is 10.15 percentage points. Subtract that from 99.0% and the end of year 30 is 88.85% of nameplate. The formula for the end of year N, when N is from 2 to 30, is 99.0% minus (N − 1) times 0.35%. If the limited warranty defines the step differently, the PDF controls.

The 560 W column uses the top of the 540–560 W range on that sheet, multiplied by the share above. Year 10 is 99.0% minus 9 steps of 0.35%, which is 95.85%, and 0.9585 times 560 W is 536.8 W. Year 30 is 0.8885 times 560 W, which is 497.6 W. These watts are standard-test nameplate floors. They are not operating power on a hot roof, and they are not annual kilowatt-hours.

A second schedule, used here only as arithmetic, shows why the slogan is not enough. Suppose another document says first-year loss of 2.0% and then 0.45% per year. End of year 1 is 98.0%. Twenty-nine steps of 0.45% are 13.05 percentage points. End of year 30 is 84.95% of nameplate. On the same 560 W label that floor is 475.7 W. The gap versus 497.6 W is 21.9 W per module at the test condition, before measurement rules. Both documents can still be titled “30-year linear.” Compare the two rates and the year-30 watts, not the title.

Apply the 1.0% / 0.35% pair only where that model’s warranty or datasheet prints it. A 100 W to 700 W catalog contains more than one outline. A rate from the three-piece TOPCon tables above is not a family ceiling for every Weltrus module. Ask for the page that names the model code you will receive.

Measurement Rules That Decide a Claim

The floor is only as strong as the test that proves a shortfall. Standard test conditions mean 1000 watts per square meter, a cell temperature of 25 degrees Celsius, and the AM1.5 spectrum. The warranty should say that this is the condition, and it should say which power is measured. For a bifacial module the usual warranted number is front-side maximum power. Rear-side gain is a site result. A bifacial factor on a datasheet, such as 80% with a tolerance band, is not extra warranted watts unless the warranty text adds them.

Nameplate is the labeled power, not the positive end of the flash tolerance. A module that left the factory 5 watts above its label does not raise the warranty floor unless the warranty says the baseline is the factory flash. Keep the label watts and the flash file, and use the baseline the PDF names.

Four measurement clauses change whether a real shortfall becomes a payable claim:

1. Stabilization. Some texts require a stated light soak, or a minimum exposure, before the official test. A warehouse flash on a new module may not be the test the warranty accepts.
2. Laboratory. The warranty names who may test: an agreed lab, a party the warrantor appoints, or any lab with a stated accreditation. A test from outside that list can be rejected even when the number is low.
3. Uncertainty. Some texts require the shortfall to exceed the lab’s stated measurement uncertainty before a claim starts. A module measured slightly under the floor can still fall inside that band. Read the sentence. Do not assume a 1% miss is automatically payable.
4. Who pays. The text says who pays for removal, shipping, and the test when the module meets the floor, and who pays when it does not. That cost belongs in the project model, especially for rooftop arrays where module removal is labor.

Serial-level evidence closes the loop. The claim needs the serial on the module, the same serial on the packing list or flash report, and a way to show that serial was part of the warranted shipment. A photo of a label that does not match the bill of lading is a weak file.

Exclusions and the Claim File

Power loss has many causes. The warranty pays for the causes it lists and refuses the causes it excludes. Read the exclusion list against the site you are actually building, not against a generic rooftop.

• Installation outside the manual. Clamp positions, torque, maximum system voltage, and the series fuse rating are usual boundaries. A mounting method the manual does not allow can void both terms.
• Damage in transport or handling after the risk point in the sales contract. The warranty and the Incoterms clause should name the same point.
• Unauthorized repair or a removed, altered, or unreadable label.
• External stress the text excludes: extreme hail beyond the stated test, fire, flood, or a system design that forces continuous shade and hot spots.
• Soiling, vegetation, and lack of maintenance when the text treats them as owner obligations rather than product defects.
• Use outside the stated application, for example a mobile or marine mounting when the warranty is written for a fixed array.

Light-induced degradation, potential-induced degradation, and degradation at elevated temperature and light are mechanisms buyers ask about by name. They are inside the power warranty only when the text says so, or when they appear as a loss of maximum power under the stated test and no exclusion removes them. A datasheet line that claims resistance to potential-induced degradation is a design claim. It becomes a warranty fact when the limited warranty covers the resulting power loss.

The claim file is a procedure with a clock. Typical contents are the serial, the commercial invoice, proof of the start date, the limited warranty version, photographs, and the lab report. The notice window may be a number of days after you discover the shortfall. Missing the window is an independent reason for refusal. The remedy is whatever the PDF lists: repair, replacement, or a payment tied to the power shortfall. A payment formula that uses the then-current module price is different from a formula that refunds the original price. Copy the formula into the bid comparison. Two “replacement or refund” sentences can move different amounts of money.

Documents to Lock Before the Purchase Order

Attach documents, not adjectives. Before the purchase order is signed, the file for that model and revision should contain all of the following.

1. The limited warranty PDF with a version date, the warrantor’s legal name and address, and a model list that includes the code you will receive.
2. The power schedule as a formula or a year-by-year table, with the first-year cap and the annual step visible. A brochure sentence is not this document.
3. The product term on the same PDF, read as its own number of years.
4. Start date, territory, and transfer. The destination country is included. Assignment to a later project owner is either allowed or expressly refused.
5. Measurement method: test condition, front side or both sides, stabilization, accepted laboratory, uncertainty rule, and who pays.
6. Exclusions and the claim remedy, including the notice window.
7. The IEC 61215 and IEC 61730 evidence for the same model family, with the report holder named. Keep this file next to the warranty. Do not substitute one for the other.
8. Serial and flash format you will receive with the shipment, so a later claim can match a label to a bill of lading.
9. Any insurance certificate the supplier offers as warranty backing. A sentence that says “insured” is not a certificate. If there is no policy, record that absence. Do not fill it in.

When two quotations both say 30 years, put the year-30 watts, the product term, the warrantor, and the remedy in four columns. Price per watt comes after those columns agree. A lower module price with a lower year-30 floor, or with a warrantor you cannot identify, is a different commercial offer.

What This Schedule Does Not Decide

• It does not set energy yield. The floor is power at a stated test. Weather, soiling, shade, temperature, bifacial gain, and inverter limits sit in the yield model. Keep the warranty floor out of the specific-yield cell unless the warranty itself promises energy.
• It does not replace IEC 61215 or IEC 61730. Qualification evidence and the warranty schedule are both required. A certificate without a limited warranty, or a warranty without a matching model on the certificate, is an incomplete file.
• It does not apply one Weltrus rate to every wattage from 100 W to 700 W. The 1.0% and 0.35% per year figures above are the rates printed for the stated three-piece TOPCon power ranges. Other models need the page that names them.
• It does not add rear-side gain to the front-side floor. Bifacial energy is modeled from the site. It enters the warranty only if the warranty text says so.
• It does not choose the mounting system, the string length, or the inverter. Those decisions use voltage, current, load, and the installation manual. The warranty then records the boundaries those choices must respect.

Frequently Asked Questions