How long do solar panels last? In a nutshell, quite a while

An average solar panel’s performance warranty ensures that the modules will produce at least 90% of their rated output in year 10 and at least 80% in year 25 or 30. In fact, it is closely related to solar panel degradation rate, which will be discussed further in the article.

An equipment warranty, also known as product or workmanship warranty, typically guarantees 10-12 years without failing. It covers the integrity of the panel itself and protects you against defects in material, premature wear and tear, as well as environmental and workmanship issues. The manufacturer may choose to repair or replace the product at their discretion.

This type of warranty normally does not cover the cost of labor to diagnose the problem and/or replace the equipment. Neither does it include the shipping costs to deliver replacements on site. Contact your solar installer to learn if these costs can be covered by their workmanship warranty.

A warranty will only remain in force as long as your system is designed appropriately. For example, if your inverter isn’t a good match for your system, it may short-circuit your equipment, and the warranty will not cover the damage. Read How to size a solar system for your home and follow our step-by-step guide to design a perfect system. You may also void your warranty if you have your panels repaired by an unlicensed worker or if you accidentally step on them while walking on your roof.

Degradation rate is the rate at which solar panels lose efficiency over time. For instance, if a panel has a degradation rate of 1% per year, it will be 10% less efficient after 10 years of operation.

According to the National Renewable Energy Laboratory (NREL), the average solar panel degradation rate is around 0.8 percent. Of course, this metric largely depends on the materials and technologies used by the manufacturer and varies from 1% to 0.5%. Some premium manufacturers like Panasonic, SunPower or Q CELLS, offer degradation rates as low as 0.3%. Solar panel degradation rates are constantly improving as solar panel technology gets better over the years.

There is a very small catch to linear warranties – they are only linear starting from year two. During the first year of operation the performance decrease may be as high as 3%, and even the best manufacturers set the target at about 2%. Most of the decrease happens immediately after the panels are put in operation. The cause is silicon impurities. The microscopic fractions of oxygen actively bond with boron during the first few hours of sunlight exposure, causing most of the year one efficiency drop.

To make the idea of degradation rate crystal clear, let’s take a 300W solar panel as an example. Given 0.8% annual degradation rate and a 3% first year drop, in year two such a panel will operate at 97% of its original output, which is 291W. In year three its efficiency will be 96.2%, meaning 288.6W output. So, to determine the projected output of your solar panels after a certain number of years, you can multiply the degradation rate by the number of years after year one and subtract that number, together with the year one drop, from 100%.

Actually, solar panel degradation is what performance warranty is about. But, as you might notice, performance warranty never guarantees 100% efficiency. Why is it so? Solar energy does have no thermodynamic limitations, since it is converted directly into electrical energy avoiding a step involving heat. However, there are still some issues limiting solar panel efficiency, such as indirect band gaps, resistive losses, etc.

Generally, solar panels are pretty easy to maintain because they are designed to withstand extreme weather conditions and all types of precipitation, such as snow, hail and wind. Moreover, they hardly ever need repairs since there aren’t any moving parts that could break down.

Even though solar panels don’t require daily spit and polish, you can extend their lifetime by routine care and quality maintenance. To maintain and extend the lifespan of your solar modules, you can follow these simple rules:

• Work with a trustworthy solar installer that provides routine maintenance checks. They can alert you to any quality degradation in the panels or any issues with the racking, wiring, etc.
• Pay attention to other elements of your solar system (inverters, batteries, optimizers, etc.). Make sure they are all of matching technical characteristics and work properly without any abnormalities. Since everything is interconnected in your system, failure of practically any component might damage the panels.
• Keep your panels clean and wash them with water if they are dirty. When dust or sand isn’t removed for too long, it can cause microcracks and scratches on the solar panel. They, in turn, if left unchecked, can multiply and break the panel.
• Remove any debris, such as fallen tree branches, and snow loads. They are even more harmful to solar panels than dust or sand because they put more pressure on PV modules. Moreover, snow left on the panels can freeze and cause the panels to get microcracks from extreme cold.

Maintenance does influence how long solar panels last on average. The tips above will help you reduce any strain on the solar panels and ensure that your panels harvest as much sun as possible and last for decades.