content: While this is true, it's an important component in the system, that so far, has been lacking with regard to efficiency.  Having a unit to efficiently store and deliver individual solar/wind generated power will go a long way to having people begin to choose to lean as heavily on the grid. A 30k system that pulls you off 90% of the grid would pay for itself before a normal mortgage is paid off. It would effectively reduce a $150 monthly bill by $135.