When purchasing a solar energy system, make sure that you read the manufacturer's warranty carefully. This is a very expensive item, and you want to know that you will be able to get a replacement in the event something happens to it. You should purchase an extended warranty if the one that is offered is very limited.
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Be sure mountings on solar energy panels are engineer certified for your area. For instance, if if you're in an area that gets frequent cyclones, the mountings need to be cyclone rated. High-quality systems will be wind certified to ensure they don't blow away in a huge wind storm. Mounting is an important part of the system and not all suppliers regard them that way. Stay alert when buying your system to make sure they have proper certifications.
Carefully consider the types of solar panels you plan on having installed. Long ago, if you didn't have enough roof space, you'd need very expensive high efficiency mono-crystalline panels. There are now more advanced polycrystalline panels and even thin film panels. If you've got enough roof space, you might wish to look at the size of the panels in relation to their output capacity to avoid having insufficient panels that you need more of later.