Distributed energy resources (DERs) can provide a number of functions to be used in grid services with proper establishment of control and communication systems. However, there are neither general standards for vendor independent integration of these assets in management activities, nor common consideration of specific flexibilities that different DERs have. This paper investigates characterization and comparison of individual power and energy management flexibilities of different types of distributed energy resources. Emerging DER capability identification approaches are used to highlight contrasting differences between several energy storage and distributed generation options. Experiments were conducted in a low voltage test facility to compare flexibility limits using the same control and communication infrastructure.