The increasing penetration of consumer-side distributed energy resources (DER) presents new opportunities and challenges for modern power systems. This chapter explores the management of consumer-side DER, focusing on their integration and coordination, and their impact on grid reliability, sustainability, and flexibility. Key topics include the role of DER in providing ancillary services such as demand response, voltage regulation, and frequency stabilization, alongside their contribution to power system inertia and flexibility. The chapter also examines the technological and economic implications of DER deployment, including risks associated with uncontrolled integration. A detailed analysis is presented on the mechanisms for DER coordination, emphasizing the role of aggregators, edge devices, and home energy management systems (HEMS) in optimizing DER utilization. Information and communication technologies (ICT) for DER management, including standardized protocols, interoperability challenges, and cybersecurity, are critically reviewed. Additionally, this chapter highlights the potential of peer-to-peer energy markets and flexibility services to empower end users, reduce energy costs, and enhance system resilience. By integrating consumer-side DER into grid operations effectively, stakeholders can unlock significant economic and environmental benefits. However, achieving this requires a robust regulatory framework, advanced forecasting tools, and seamless information exchange between DER, utilities, and market operators. This chapter provides recommendations for addressing these challenges and leveraging consumer-side DER to foster a more flexible, sustainable, and resilient energy system.