usually the small size wind turbines/solar PV panels need a back up battery for charging - from that only AC current is drawn via inverter. This need frequent maintanace for battery and relacement after 2 years. Now I have a new latest technology for using the solar PV panels and wind wind turbines using that without battery bank and don't need the battery at all. We can online get the solr/wind turbine DC current into 220V 50 HZ A/C currentand that can be parallely connected to the govt. grid. system to the home/office/factory. So the electricity bill be drastically reduced. Bit expensive initally but really worth full.