In recent years, solar panels have significantly dropped in price. They are now at a point where, “solar PV is now cheaper than oil and Asian LNG (liquefied natural gas)”. What is more, “the cost of solar PV modules could fall beyond most expectations in coming years — and reach a cost of just 25c a watt by 2020”. The price of solar panels, however, remains high, especially if your daily electricity consumption is high. Buying secondhand or cheap solar panels kits often appears to be an attractive option.
Is it, however, really beneficial to you? Why do people buy secondhand solar panels? Why would someone make solar panels himself, rather than buy them? This blog post is written to provide answers to these questions, as well as to disprove some common myths about cheap solar panels.
Decreased lifespan of cheap solar panels kits
The required lifetime of the solar panels you will use in your solar panel system depends on the expected lifespan of the system.
For example, if you need small and cheap solar panel kits to provide power to a simple device or a recreational vehicle, a cheap panel is the better option, rather than buying an expensive branded solar panel. If you buy a cheap solar panel, you are likely to save up to 50% off the price, compared to buying a branded panel. Even if in the beginning the stated parameters turn out to coincide with the real parameters, you could expect some degradation in performance.
The worst, however, is that no one can tell you how much further panel efficiency is going to degrade. Therefore, you might encounter some unpleasant surprises.
So if you choose to buy cheap solar panels, you should buy more powerful ones (that is, of higher rated power each) than you need. A recommended percentage is 15 to 20% higher rated power. Certainly 15–20% more rated power means a higher price, but you still save money and, what is more important, this is a fair guarantee that your system will not underperform years after installation. The warranty of cheap solar panels is usually only extended to one or two years, rather than the typical 25–30 years warranty standard with new panels. If you’re buying a large-area panel or a solar panel that is to be installed on a vehicle, you should choose a panel made of tempered glass. Tempered glass is 7–8 times more robust than plate glass and is better protected against both physical damage and water infiltration.
Degrade in efficiency of cheap solar panels kits
Secondhand panels usually have much lower efficiency. This means not only that you cannot make a precise enough sizing of your solar panel system, but also that you need a greater (how much ‘greater’ no one can tell!) space to install the modules to generate the same amount of power, compared to the case of using new panels.
Warehouse-stored secondhand solar panels do not degrade in efficiency over the years, compared to panels exposed to direct sunlight.
During the panel survey, you should ask about panel’s initial efficiency and how much the initially rated power got reduced. If the initial efficiency is said to have been reduced by 20%, you should multiply the area required for solar panel installation by 1.2. Therefore, to keep the system output equal to the initially planned one, you have to increase the installed rated Wp power by 20%.
This means adding more panels of the same type. If the initial efficiency is said to be reduced by 10%, you should multiply the calculated solar panel area by 1.1, thus adding more panels to compensate for the reduced efficiency.
Remember the golden rule about solar panel assembling: Mix neither solar panels produced by different vendors, nor solar panels produced by the same vendor but of different characteristics, or panels belonging to different series!
Branded vs. unbranded secondhand panels
Certainly, not all solar panels are designed to be equal. It is always better to buy a branded panel than an unbranded one, bearing in mind that unbranded panels might turn out to behave in a way other than expected — for example, resulting in a shorter lifespan and/or less energy generated. If you are implementing a solar panel system that is to operate for a long enough period — 20 years or more — you should choose branded panels for it. If secondhand panels come from a well-known brand, they are often a really good value for the price. A branded secondhand panel might be able to provide service for 25 years or more.
This is because no one actually knows how much longer the life of a branded solar panel could last. Practice has shown that panels manufactured 30 years ago have a real power output of up to 90% of the original rating.
Regarding the type of solar panels, it is recommended to choose monocrystalline ones, as this technology has been proven over time, and you can still find solar panel systems equipped with these panels working between 25–40 years, with performance degradation of about 20%. The second best option is to choose branded polycrystalline solar panels. But since this is a relatively newer technology compared to monocrystalline one, nobody can predict their performance degradation over time.
Currently, it is not advisable to buy secondhand thin-film (amorphous) panels since this technology is relatively new, and there is not enough statistical data on the degradation of their performance over time.