This paper presents an economical study of the effect of demand-side management (DSM) by implementing a PV system on bulk customers on all elements of the electricity sector including their impact on grid operations and planning in the Kingdom of Saudi Arabia. Demand Side Management is assumed to be applied in Riyadh, as a case study, using the concept of load shaving by photovoltaic system implementation for bulk customers as a segment to manage the demand during peak period. The Time of Use (ToU) tariff model is developed and incorporated in this study. Then an economical study is carried out to calculate the money-saving by Saudi Electricity Company as the impact of load shaving at peak period. Moreover, the paper considers the economic impact of the load reduction influences on the long-term forecast and hence the investment in the conventional generation power plants. Finally, the study determines how much is the saving of electricity bills for bulk customers due to PV implantation including the expected payback period to support the usefulness of adopting DSM for the electricity sector in KSA.