So, you've got your parts list (see our larger articles for some recommendations), and you know where you want to put the system, and where the batteries are going to live.  It's time to comparison shop.  Comparison shopping can save you substantial amounts of money on buying a solar electric system; you can often find companies that are upgrading their systems and are willing to sell inverters and controllers at a deep discount; we've even had a few cases where they were free if we showed up on a weekend with a truck.  Make sure the parts are compatible with your overall plan, but don't be afraid to buy used; about the only systems that might be iffy if bought used are the solar arrays themselves if they're over a decade old.