The solar panel inverter is a fully automatic device. One of the many advantages to a solar installation is that it is very low maintenance and requires no attention.
When sufficient sunlight or daylight is available during the morning, the inverter will start up, the unit goes through some safety tests and then will start up and produce electricity.
When grid electricity is lost, the inverter will detect this and shut down for safety reasons. It will self-detect when electricity is present again so it can reboot.
When during the evening there is not enough sunlight or daylight left, the inverter will shut itself down. The electricity you then consume comes from the grid or possibly a battery.