Solar Panel Warranty Guide: How Long Will My System Last?

Solar Panel Warranty Guide: How Long Will My System Last?

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Solar panel warranties can be a bit of a headache to understand. They’re split into two categories (performance and workmanship), each with different warranty lengths and areas of coverage.

If your system stops producing the way that it should, it’s not always clear whether you’re covered. Since solar is a big purchase, it’s important to understand how solar warranties work to protect your investment.

For your peace of mind, here’s everything you need to know about how warranties work in the solar industry.

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How Solar Panel Warranties Work

What is a “workmanship warranty?”

The workmanship warranty on your solar panels covers any physical defects that stem from manufacturing errors. Some examples might be:

  • Imperfections in the frame or glass
  • Loose junction boxes
  • Faulty connectors
  • Bad cells or damaged cell connections
  • Defective backsheet

If the panel malfunctions due to a manufacturing defect, that is covered under the workmanship warranty.

What is a “performance warranty?”

The performance warranty guarantees your panels will produce near their rated output over the life of ownership.

Panel production naturally degrades over time, but it happens at a very slow rate—less than 0.5-1% production loss per year. While production loss will occur for any panel, the performance warranty ensures it happens at a reasonable rate.

For example, these Mission Solar panels output 360 watts. The warranty accounts for a 3% drop in production in the first year, then 0.7% every year after that. After 25 years, your panels should still produce 288.72 watts (80.2% of their original 360W rating).

A few premium panel manufacturers like LG offer better warranties (87% after 25 years) because their panels degrade at a slower rate.

The performance warranty ensures your system’s output is reliable and consistent. If a panel’s output suddenly falls off a cliff, it would be covered for replacement under the performance warranty.

Linear vs. Step Warranties

Most companies offer a linear performance warranty. Mission Solar’s guarantee of 0.7% production loss every year is an example of a linear warranty: it progresses at a constant rate year-over-year.

Some manufacturers offer “step warranties” on their panels. Under this warranty structure, the performance guarantee stays at a flat rate and steps down at certain milestones.

For example, certain Astronergy panels are covered at greater than 90% efficiency upon purchase, which steps down to 80% at year 10 and stays there until year 25.

Step warranties offer less coverage for under-performing panels. For example, if your panel is producing at 85% output in year 11 of ownership, you would be entitled to a replacement under a linear warranty, but not under a step warranty.

In general, companies have moved away from step warranties, but you may still find them offered on older modules, so it’s something to look out for.

How Long Do Solar Panel Warranties Last?

Most solar panels come with a 25-year performance warranty. This is the industry standard from Tier 1 manufacturers at the moment.

Workmanship warranties cover a shorter timeframe: Mission Solar and Astronergy offer 10-year workmanship warranties, but that number varies by manufacturer.

When the warranty expires, that doesn’t mean your panels stop working! They’ll still be producing power, albeit at a reduced rate. A 360W Mission Solar panel should still produce 288W after the 25-year warranty is up.

They can still be used to power your appliances, but they’re no longer covered if the production starts to taper off. A study by NREL (National Renewable Energy Laboratory) shows that 4 out of 5 panels outperform their warranty, so it’s likely your system still has some life in it after the 25-year mark.

What Are Third Party Warranties?

25 years is a long time. What happens if you need to put in a warranty claim, but the company that made your panels has gone out of business?

For that, certain manufacturers like SolarWorld offer third-party warranties and other forms of warranty protection. In case of bankruptcy, the warranty transfers to a 3rd party insurer who continues to honor replacements and refunds under the original warranty.

Tier 1 manufacturing companies are quite stable, but a lot can happen in 25 years. This provides an extra layer of protection so you don’t get hung out to dry.

Solar Inverter Warranties

So far, we’ve only covered the warranties on solar panels. But there are other parts of your system covered under their own product warranties.

Panels have the longest warranty of the bunch at 25 years. Inverters and batteries generally have shorter warranties.

Here are the warranties for the inverters we supply:

If you opt for a string inverter like the Sunny Boy or HD-Wave, you should factor at least one inverter replacement into the lifetime cost of ownership.

Most inverter manufacturers offer extended warranty programs to cover these replacements. These cost a little bit extra up front, but it’s cheaper than replacing the inverter out of pocket down the road.

Solar Battery Warranties

Battery warranties are a bit trickier. Flooded lead-acid batteries cost less up front, but have regular maintenance requirements to keep them in working order. These batteries have the shortest warranties, and if you fail to perform regular upkeep, the warranty will be voided.

Sealed lead-acid batteries and lithium batteries cost more, but the maintenance requirements are removed and they have longer warranties to match the higher price tag.

Sample battery warranties:

  • Crown flooded lead-acid batteries: 3 years
  • Fullriver sealed AGM batteries: 7 years
  • Discover lithium batteries: 10 years

Read our in-depth cost comparison of lead-acid vs. lithium batteries.

Another thing to note is that the true lifespan of your batteries can vary greatly depending on the application.

Battery life is measured in charge cycles. The act of discharging your batteries (to power your appliances) and recharging them from your solar panels counts as one cycle. For example, this Fullriver AGM battery has a cycle life of around 1250 cycles at 50% depth of discharge.

In off-grid applications, your battery bank is your primary source of energy. You’ll be cycling it on a regular basis to provide uninterrupted power to your property. With heavy use, you’ll reach the expected cycle life at a much quicker pace.

However, if you’re using batteries as energy storage for a grid-tie property, they’ll see less frequent use—only at certain times of day to offset high time-of-use rates, or as backup power during a grid outage.

Though you might use the same exact battery, it will have a longer lifespan in this application because it is not constantly cycling.

Factors That Can Void Your Warranty

One last word of caution: warranties only cover your equipment when your system is properly designed and cared for.

All warranties carry clauses that essentially boil down to this: “if you use the equipment improperly, we’re not responsible for the damages.”

For example, string inverters have a voltage range in which they can operate safely. Your system must be sized so that panels supply the right amount of voltage to your inverter, a process known as string sizing.

If your panels send too much voltage into the inverter, it can fry your equipment. That damage would not be covered under warranty because the manufacturer would consider you to be at fault.

Learn how we calculate string size here (warning: lots of math ahead).

Similarly, battery banks must be sized properly so that they charge or discharge at a healthy rate. Completely draining lead-acid batteries when you cycle them will reduce their lifespan, another mistake that would not be covered under warranty.

This is where we come in. Our complete solar systems are packaged with these restrictions in mind, so you can be sure you’re getting a system that’s properly sized. If you’d like to put together a custom system, you can also consult with an experienced solar designer to ensure your system is up to code.

Download our free solar panel buying guide!

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