A solar panel charges a storage battery. A control circuit monitors the battery's voltage. When the battery is fully charged, the circuit automatically turns on a power inverter and switches the appliance from running on grid power to running on the energy stored in the battery.
In the original circuit, a 555 timer IC was used to disconnect a battery from the solar panel when its voltage gets too high (to prevent it from over charging). In my design, the control circuit connects the battery to an inverter and an output circuit when the battery is fully charged.