A grid-connected device for electricity storage can also be classified as a DER system and is often called a distributed energy storage system (DESS). DERs are small modular energy generators that can provide an alternative to traditional large-scale generation. What are DERs? Distributed Energy Resources (DERs) are small, modular energy generation and storage. What energy storage technologies are used as distributed energy resources? How do DER systems work in conjunction with electric grids? What are the benefits of DER? What are the challenges of DER? What are distributed energy resources (DER)? Distributed energy resources, or DER, are small-scale. Distributed generation, also distributed energy, on-site generation (OSG), or district/decentralized energy, is electrical generation and storage performed by a variety of small, grid -connected or distribution system-connected devices referred to as distributed energy resources (DER). This fundamental aspect of distribution fundamentally shifts how we conceptualize energy management.