Effective integration of distributed energy resources (DER) with distribution systems depends greatly upon the availability of models needed to plan and study these devices as part of the overall system. The rapid evolution of DER technologies and applications, however, poses a challenge for distribution planners and others who must ensure system studies accurately capture novel behaviors and interactions that can occur with DER interconnection. Quasi-static time-series (QSTS) simulations are one tool increasingly being used by the industry to study DER and active distribution systems. While the development of QSTS models and simulation capabilities have generally kept pace with DER technology advancements and study needs, often derived models are custom and highly specific to a given application. The lack of standardized models has also resulted in numerous model definitions, inconsistent terminology usage, and models that are overly complex. This chapter outlines a framework for defining and building a robust portfolio of DER benchmark models for QSTS simulations of electric distribution systems. A benchmark model for PV is also provided to illustrate the framework’s application. DER models derived using this framework offer a common reference for distribution engineers, vendors, academia, and other industry stakeholders to understand and verify the performance of existing models, as well as provide a foundation for standardization of industry models.