UL Approval- If you build your own solar system and see visions of grander in your eyes; you might want to take a step back. Tying to the power company grid or called grid-tye, just will not happen without a UL label on each solar panel, plus the equipment associated with the panels. Obtaining a UL sticker is almost impossible unless you are God!
Structure of Solar Panels- How your panel is made is a real concern. If you are building your own panels then you need to make sure they will last. They should be made with strong aluminum frames using at least 1/4 inch tempered glass. In my experience, building solar panels with plywood is a big mistake. They just will not last in the weather elements.
Encapsulation of the cells- When you build a quality solar panel, you need to seal the cells by encapsulating them with a special sealer made especially for solar panels. If you look at a good commercial panel, you will see how they are sealed which allows cells to flex with temperature changes.
Electrical integrity- Make sure that all your solder joints are done properly so that there are no cold or loose electrical connections. If your charge controller does not have diodes then you will need one at each panel you build. The reason for the diode is to block the electrical current from trying to return back to the solar panel, thus draining your batteries.
Mounting of your solar panels- When you get ready to mount your solar panels you need to think about how you want to mount them. My concern here again is the longevity of your system. I know there are mounting systems that are available but being electrical construction minded I suggest using 1-5/8 inch uni-strut channel available at electrical supply houses as will has your local home supply store. It comes in either 10 or 20 foot lengths. Mounting the channel parallel allows you to mount your panels in straight rows. It also allows air flow below your system keeping your system at a lower temperature.
As you can see there are concerns about building your own solar panels. I must stress again that all these people who tell you that you can make your meter spin backwards, are not telling you the whole story. Like I told you before, tying to the electrical grid is not allowed unless your system has been UL approved and inspected by local authorities. One thing power companies do not want is power being fed back into there grid. All grid tie systems must be equipped with a automatic system that will disconnect your solar from feeding back during power outages.