One of the most frequently asked questions about solar panels is their life expectancy. According to Nigel Calder, the life expectancy of a solar panel depends on how well it is built and installed.
Importance of Proper Construction and Installation
In the home power world, solar panels can last for 25-30 years, and many of them are warranted to maintain 80% of their rated output after 25 years. It’s different on boats. Although some panels last a long time (Nigel’s current panels are 16 years old), many fail within a year or two. Poor construction and inadequate installation are the principal culprits. Especially with the popular semi-flexible panels, which can be installed on curved cabin tops and over biminis and other canvas structures, if the panel itself is not adequately sealed delamination and water penetration will occur, and if it is not securely mounted (for example, flexing on a canvas bimini) cell cracking and intercell connection failure will occur.
Buying Reliable Solar Panels for Marine Use
There are standards that solar panels have to meet in the home power market with respect to life expectancy and reliability, but when it comes to marine use, even if those same panels are used the standards no longer apply. The operating environment is much tougher and there are too many additional potential failure modes, including corrosion and movement, which makes the panels more vulnerable to damage.
To ensure the reliability of solar panels in a marine environment, Nigel recommends buying from a recognized marine brand with a decent warranty. These will be expensive, but generally buying cheap panels is more trouble and expense in the long run. Even with ‘high end’ panels there have been batch failures caused by manufacturing defects. So buyers should look for a minimum five-year warranty, and a 10-year warranty if possible (this is rare). The warranty needs to be for a full replacement and not prorated - i.e., if the panel fails towards the end of the warranty it is still replaced instead of receiving a small percentage of the purchase price.
Solar Panels as a Cost-Effective Investment for Boats and Homes
In spite of the potential problems, for any offshore cruising boat that otherwise would have to run a fossil-fueled engine to generate electricity for house loads, solar panels are almost always the most cost-effective way to create that electricity. Although solar panels require a considerable initial investment, the more a boat is used the sooner this pays off. There are additional obvious lifestyle benefits (e.g., reduced engine run time) and less obvious systems benefits (e.g., extended battery life expectancy through operation in a higher average state of charge).
If you want to get more into detail about solar panels, their controllers (including the latest generation boost controllers), and fully optimized installations, check out our courses on Marine Electrical Systems, particularly the bonus module on alternative energy sources.
If you're interested in recent advances in batteries and solar, you may also check out Nigel's talk on that topic.