Do I need batteries?
Depends on the system being installed. Grid tied systems don't normally use batteries, however a battery back up system can be designed. These batteries would power a dedicated panel or load in the event of a blackout. Off grid systems, on the other hand, almost always have batteries, unless another energy storage is used. This could include pumping water uphill during the day, then use a micro-hydro type design during the night.
Grid Tied System