A Battery Backup System will turn you Solar Power System into 24/7 Solar Power Generator.  This is the biggest step towards energy independence that you can take.  It will provide security for you and your family in emergency power shortage or outage situations.  Imagine just flipping a switch during a power outage and instantly having power.  It is energy independence at work.  Like most things that give us independence there are costs.  A Battery System will close to $7000 to your bottom line and reduce your systems overall efficiency by 2-3%.  However with the financing options that are available today you can have the complete system built into a low monthly rate that equals your current power bill.  So you can have energy independence for the same money that you are already paying to the power company.  Pretty good trade off and well worth the investment.