Solar panels like any other product are Not the same, as some solar panels manufacturers use the high quality equipment and materials in manufacturing process, while others do Not. The used high quality materials will lead to high solar panels performance and high reliability. Those solar products manufacturers who always conduct researches to develop their solar panels manufacturing process are absolutely the best for us to buy from even their prices may be a bit higher than others.
Mainly, the solar panel is manufactured of a different composite of chemically treated silicon cells, glass, aluminum, plastic, sealants and interconnected wiring. And for whole solar panel life, it will be existing outdoor and exposed to harsh environment of direct sun and rain, which will affect certainly on solar panel materials, changing its chemical properties, and perhaps solar panel internal materials react to each other and create new compounds and chemicals which affect their performance as well. Also, due to harsh change in external environment, the solar panel elasticity will change which will affect badly the tension and stress of different materials they do on each other.
That is why the solar manufacturers who are well understanding materials properties science and investing in related researches are able to anticipate these changes occur over the entire solar panel life time and provide production solutions to reduce its side effects or even eliminating it.
Of course such experienced solar panel manufacturers who are well understand these issue and provide solutions during manufacturing process will have ISO accreditation and will have quality and control assurances showing them in their marketing and promotional materials.
Such manufacturers usually have well know brands which are famous in the solar panel market, with long experience and presence. And those who you have to search for when deciding to purchase and install your new solar photovoltaic system, because such solar panels brand will make big difference in your whole PV system electricity generation, reliability, high quality performance and longer life span.