PV systems produce energy at different rates depending upon the time of the year. As the intensity of radiation and angle of the sun varies through the seasons so does the power output of the system. The highest solar generation during the day is usually from 11am to 4pm. So, during this time, the PV system may generate excess electricity than required.
For large consumers of electricity that include businesses, manufacturing operations, and institutions, etc the electricity consumption varies throughout the day where sometimes the electricity demand will be high and sometimes the demand will be low. To manage this fluctuation utility provider, vary their electricity pricing throughout the day.