Distributed energy resources are small, modular, energy generation and storage technologies that provide electric capacity or energy where needed. DERs are physical and virtual assets deployed across the distribution grid, typically close to load, and usually behind the meter, which can be used individually or in aggregate to provide value to the grid, individual customers, or both. Examples include solar panels, energy storage, generators, electric vehicles, and combined heat and power systems that typically offer less than 10 MW of capacity. Outputs from DERs can offset the need for supply from a centralized system. Thus, DERs can offer greater customer choice and may present opportunities to optimize overall system investments and provide a range of grid services. Increased use of DERs creates a more decentralized electricity system and changes in the traditional dynamic between local distribution systems and the larger transmission system. Source:  NREL