The Modular Energy System Architecture (MESA) Standards Alliance is an industry association of electric utilities and technology suppliers. MESA’s mission is to accelerate the interoperability of distributed energy resources, in particular utility-scale energy storage systems, through the development of open and non-proprietary communication specifications. MESA has developed and published two specifications: MESA-DER (formerly MESA-ESS) and MESA-Device/SunSpec Smart Storage. The MESA-DER specification defines the mapping between the commonly used utility SCADA protocol IEEE Std 1815 (DNP3) to the IEC 61850-7-420 DER information model, thus creating an interoperable profile of DER functions, monitored information, and control commands. This MESA-DER interoperable profile was incorporated into and is defined in the DNP3 Application Note AN2018-001. The MESA-DER specification also supports all the IEEE Std 1547 and CA Rule 21 DER functions as well as additional market-based DER functions to support safe, reliable, and efficient operations. MESA is partnering with the Pacific Northwest National Labs (PNNL) to develop a testing and certification program for the MESA-DER specification. MESA’s Testing and Certification Working Group, led by PNNL, is comprised of utilities, vendors, and other stakeholders with the goal of improving interoperability, reducing cost to integrate, and providing confidence that systems and components interact as expected. MESA’s presentation will provide an overview of the MESA-DER specification and provide an in-depth overview of the testing and certification program.