Chapter IV Key Takeaways

Once a project’s means of safely and reliably controlling export have been established, as described in Chapter III, the project can be screened and/or studied with the assumption that it will control export as specified. However, because most interconnection procedures have been drafted without export controls in mind, this means that the screening and study processes need to be updated to specify how limited- and non-export projects will be reviewed.

In Chapter IV: Evaluation of Non-Export and Limited-Export Systems During the Screening or Study Process, the Toolkit provides background on the typical interconnection technical review process today, explains how the technical review of export-controlled systems can change, and provides recommendations for how interconnection screening and study processes can be updated to recognize these controls.

Recommendations for Evaluating Non-Export and Limited-Export Systems During the Screening or Study Process:
1. When an interconnection application is submitted, interconnection rules provide the utility with a period of time to review the application for completeness and verify the screening or study process that the application will be first reviewed under. Interconnection application forms should be updated to include information about the ESS and, where export controls are used, the type of export control and the equipment type and settings that will be used. During its completeness review and once screening or study commences, the utility should verify that the equipment used is certified, where necessary, and/or is otherwise acceptable for the intended use. The utility should also verify that the export control methods used meet the criteria identified in the export control section of the rule, as discussed in Chapter III.  

2. In determining eligibility limits for Simplified and Fast Track processes, interconnection procedures should reflect Export Capacity, not just Nameplate Rating, in the screening thresholds.  

3. Interconnection applicants should be permitted to use the Simplified process for screening purposes for certain inverter-based projects if the Nameplate Rating does not exceed 50 kilowatts (kW) and the Export Capacity does not exceed 25 kW.  

4. Some interconnection screens may need to be modified to distinguish between the Nameplate Rating and the Export Capacity of a project in order to accurately evaluate the distribution system impacts of export-controlled systems. Each interconnection screen is designed to evaluate whether there is a risk that a proposed project will cause a particular type of impact on the distribution system. Some of these screens evaluate a project’s likely impacts based upon the “size” of the project, which is generally assumed to refer to the Nameplate Rating of the project. In the case of limited-export storage systems, using Nameplate Rating instead of Export Capacity can result in an overestimation of the project’s impact. Chapter IV identifies screens in which Export Capacity is appropriate to use when assessing impacts, including in a new inadvertent export screen, as well as screens where evaluation is not impacted by export controls.  

5. As with interconnection screens, interconnection studies must take into account the manner in which a project has limited export when they assess impacts in the system impact study. If a proposed project is using one of the acceptable means of export control described in Chapter III, the utility should evaluate impacts to the distribution system using the project’s Export Capacity, except when evaluating fault current effects.       

6.  In order for the interconnection process to fully recognize the ways ESS projects can be designed and controlled to avoid grid constraints, utilities should consider operating profiles (which can include operating schedules) in their feasibility studies and system impact studies.  

A. Introduction and Problem Statement

Exported energy is often a primary consideration in the screening and technical review of any grid interconnection application. When utilities evaluate the potential impacts of a proposed DER, they evaluate a variety of different technical criteria, including voltage impacts, protection, thermal constraints, and operational flexibility.[1]Electric Power Research Institute, Analysis to Inform California Grid Integration Rules for Photovoltaics: Final Results on Inverter Settings for Transmission and Distribution System … Continue reading Most, but not all, of these factors are dependent upon how much power is exported by the DER.

With the exception of a few states where interconnection procedures have long recognized non-exporting systems, utilities typically assume that proposed DER projects always export their full Nameplate Rating, even if that DER project behavior is neither expected nor plausible. This often results in an overestimation of the impacts of a DER facility. The assumption of full export is particularly problematic for an ESS that is AC-coupled with onsite solar or other generation, as it results in the facility being studied as though the ESS exports at the same time as the solar asset, which is typically not how systems are programmed to operate because it does not make economic sense. (In some cases, there may be retail rate structures where on-peak times fall during solar production hours, making maximum battery discharge and solar exports advantageous.) However, interconnection safety review often needs guarantees of system operation even when adverse conditions are unlikely to occur and distribution system upgrades might result in excess capacity or protection. In addition, the assumption of full export ignores the ability of applicants to use managed charging as a solution to mitigate hosting capacity constraints.

In light of the growing number of areas with grid capacity constraints, some customers are choosing to install non-export or limited-export projects that can guarantee avoidance of system impacts when appropriately evaluated. Accepting the use of verified export controls and changing the way that the system is screened or studied will overcome a barrier to the interconnection of ESS that results in overestimating system impacts.

Chapter III addresses the first part of this barrier by providing recommendations on minimum requirements for export control methods. Establishing trusted methods of controlling export enables utilities to safely deviate from their default assumption that DERs export their full nameplate capacity. This chapter examines the screening and study processes on a project level when acceptable methods of export control are utilized.

As discussed in Chapter III.B, non-export systems are already included in many interconnection procedures and many state procedures already require utilities to evaluate non-export projects more efficiently in light of the fact that they do not export. Only recently have procedures begun to recognize the concept of a limited-export system, however. This chapter addresses the manner in which the technical review process should take into account a project’s export-limiting characteristics, whether they are non- or limited-export. It examines where export control enables and complicates interconnections and presents recommendations on how to alter the technical review process to incorporate equipment certified for export control into the interconnection technical review process.

Download the chapter file below to read more. Or download the full Toolkit and Guidance for the Interconnection of Energy Storage and Solar-Plus-Storage for all chapters and recommendations.


1 Electric Power Research Institute, Analysis to Inform California Grid Integration Rules for Photovoltaics: Final Results on Inverter Settings for Transmission and Distribution System Performance, (Dec. 2016); Electric Power Research Institute, Impact Factors and Recommendations on how to Incorporate them when Calculating Hosting Capacity, (Sept. 2018)