On-Grid Systems are solar pv systems that only generate power when the utility power grid is available .They are not able to function or generate electricity in times of blackouts due to safety reasons. As blackouts normally occur when the electricity grid is damaged; If the solar inverter was still feeding electricity into a damaged grid it would risk the safety of the people repairing the fault/s in the network. These are simplest systems and the most cost effective to install.  These systems will pay for themselves by offsetting utility bills in 3-8 yrs.The downside is that they do not provide power during grid outage.