What Determines the Lifespan of a Solar Panel?

01/15/2018 16:34

There's an old maxim that nothing lasts forever, and solar panels are no exception. But why do solar panels die? And how can you ensure your panels have a long, useful life?

Solar panels don't typically die in the way that batteries or other appliances do. Instead, they remain operable but stop producing the same amount of power that they did back when they were first installed. The slow, steady decline in a solar panel's energy production level is known as its degradation rate. A high degradation rate means a panel will quickly lose its ability to produce energy, while a low degradation rate implies the opposite.

A solar panel with a degradation rate of 1% per year will produce only 99% of its original power production level after one year. After 10 years, it will produce 90% of its original power output.

Most experts consider a panel dead or failed when it declines to less than 80% of its original power-generating capacity. But even this standard is up for debate, since high-efficiency panels might be capable of producing more energy than a panel of lower efficiency, even if the panel with the lower efficiency is newer and less degraded.

Choices in Solar Panel Manufacturing Techniques

Degradation rates vary considerably between panel manufacturers. Under some experimental conditions, degradation rates reached highs of 35% and lows of 1%. Overall, degradation rates have steadily declined since solar panels were first developed. According to the National Renewable Energy Laboratory, the average panel degrades at a rate of 0.8% annually. But back in the late 1980s, degradation rates were "significantly higher" than 1% per year.

The type of solar cells inside your panels can affect the panels' lifetime. Monocrystalline cells - which, as their name suggests, are crafted from a single silicon crystal - are thought to have longer lifetimes than polycrystalline and microcrystalline cells, which are created from multiple silicon crystals. And if your panels have solar cells made of amorphous silicon, cadmium telluride, or another thin-film material, they'll be even less efficient, which will shorten their lifetimes.

Manufacturing flaws are among the major causes of solar panel failure. Weak soldering joints could lead to accelerated degradation rates. Micro-cracks, present in the panel when it was installed or shipped, could also harm your panel's power generation capabilities and encourage corrosion. About 1-2% of all modules fail at the time of installation. But manufacturing flaws could linger for months or years, steadily getting worse, before causing total module failure. You can learn much more about the pros and cons of solar at PowerScout.

The choice of encapsulant also plays a role in how fast a panel will degrade. Solar encapsulants are laminate materials that increase panel efficiency and durability in harsh outdoor environments. Research shows that silicone encapsulants are associated with lower degradation rates than polyvinyl butyral and EVA encapsulants.

Solar panels that are designed for durability will have a better shot at surviving shipping, installation, and harsh weather. Panels that utilize thin solar cells that use less silicon and thin frames that use less aluminum are more prone to bend and break than panels with thicker cells and sturdier frames. Thin-frame panels and thin solar cells might allow you and the manufacturer to save money, but in the long run, these design choices could cost you.

As many panels remain at or above their original energy rating for decades after installation and both improvements in solar technology and reductions in degradation rates have made their way into PV panel manufacturing, manufacturers have responded by extending their warranties and coverage periods. Back in 1990, the average solar module warranty lasted for just 10 years. Today, the typical warranty covers panels for 25 years.

Solar Cell Degradation in Practical Applications

Once installed and operating, there isn't much you can do to extend your panels' useful lifetime. But there is some evidence that brushing your panels to remove snow can make them last longer, since the pressure from snow and ice can cause panels to bend, introducing cracks that damage the sensitive internal components.

The more serious concern with any solar energy system is not the panels themselves but the related hardware like inverters. Most inverters need to be replaced every 10 to 15 years, though microinverters may last as long as your solar panels themselves.

Off-grid solar array in McCarthy, Alaska

Above: Solar panels installed as early as 1980 - like these on this house in McCarthy, AK - are still functioning today.

Finally, the conditions under which solar panels operate can extend or slash their useful lifespans. Panels are manufactured to operate at or slightly below 25° Celsius. Panels in exceedingly hot and humid conditions will suffer from lower efficiency rates. Likewise, the expansion and contraction of the panels due to seasonal weather changes can lead to corrosion and micro-cracks. And exposure to strong winds can also increase your panels' degradation rates (presumably because the winds whip grit, rocks, and dirt against the panels with significant force).

More than 85% of all solar panels worldwide were installed after 2010, so our knowledge of what makes a long-lasting solar panel is still developing. As a result, new or experimental panel designs tend to have failure rates that are far higher than those of mature brands and models. As both rooftop and utility-scale solar panels become more common (and as new solar cell and panel types gain more time in real-world settings), manufacturers will be able to better understand how to produce panels that last even longer than those used today.

But don't let this talk of degradation stop you from installing solar panels. Improvements in module efficiency in the near future are expected to be modest, and the increased length of manufacturer warranties and performance guarantees are evidence that established PV manufacturers are confident in their manufacturing and quality control processes. In short, there's no reason to wait if you're thinking about going solar!

Excited for solar? Get a free solar quote!
Feeling creative? Design your own system!
Questions? Contact the Real Goods Tech Desk!

You must be logged in to post a comment.

to log in