Resources​

Seams

The California ISO's approach to working on seams issues underscores the importance of starting with a clear set of principles that all parties commit to, ensuring outcomes are mutually beneficial.

• Principles for Addressing Western Market Seams 02/26/2026, 10:37 AM

  This document describes a set of eight principles the CAISO developed with our partners and shared with the Southwest Power Pool (SPP) last year. They fall into three themes: reliability, respect, and mutual benefits.

Process overview

To join the WEIM, each resource must successfully execute two processes: 
     1. Integrate with the ISO Full Network Model
     2. Complete the WEIM resource onboarding procedure
The document linked below provides a detailed overview of how these two processes vary across different resources. Specifically, the document covers the procedure for new non-participating resources, new participating resources, non-participating resources converting to participating, participating resources converting to non-participating, and end dating/removing of a resource.
     - Western Energy Imbalance Market Procedure for Non-Participating and Participating Resources

1. Integrate with the ISO Full Network Model

All resources must complete the Model Submission and New Resource Implementation (NRI) process, as outlined in the Modeling Submission Checklist, prior to joining the Western Energy Imbalance Market (WEIM). Detailed guidance for completing this process is provided below.

Start Here: Checklist and Guide
Modeling Submission Checklist
This spreadsheet outlines required equipment, supporting documentation, template links, deadlines, and other key information for both CIM and Non-CIM projects.
New Resource Implementation Western Energy Imbalance Market Scheduling Coordinator Metered Entity Quick Start Guide - 2026 
The NRI WEIM SCME Quick Start Guide provides step-by-step instructions in a presentation-style format with visuals to support understanding.

FNM Schedule
Western Energy Imbalance Market Full Network Model Schedule - 2027
Western Energy Imbalance Market Full Network Model Schedule - 2026
These schedules provide the model build timeline, including all key milestones and deadlines.

Integration Templates
WEIM GRDT Template
     - Western Energy Imbalance Market Generator Resource Data Template Version 18.0

WEIM Interchange Definition Template
     - Western Energy Imbalance Market Interchange Definition Template

WEIM FNM Model Scope Template
     - Western Energy Imbalance Market Full Network Model Scope Template

WEIM FNM Late Scope Change Request Form
     - Western Energy Imbalance Market Full Network Model Late Scope Change Request Form

2. WEIM resource onboarding procedure

When a resource is ready to onboard to the WEIM, that means all integration requirements from part one are met, including Modeling requirements, Contract requirements, and Scheduling Coordinator requirements. The documents below provide the procedure and templates needed for a resource to successfully onboard to the WEIM. 

Start Here: WEIM Procedure for Non-Participating and Participating Resources
Western Energy Imbalance Market Procedure for Non-Participating and Participating Resources
This procedure helps WEIM entities submit the required onboarding documentation for new participating and non-participating resources. The procedure also applies when a non-participating resource would like to become a participating resource, when a participating resource would like to become a non-participating resource, or for end dating/removing of a resource.

Templates for New Participating or Non-Participating Resources
The following documents will be submitted via a CIDI ticket along with the WEIM GRDT, which should already be completed. 
WEIM - New Scheduling Coordinator Acceptance - Resource - Letter Template
WEIM - Resource Owner Scheduling Coordinator Selection - Letter Template
Resource Control Agreement Disclosure Form

Templates for Converting Resources
Resources converting from Participating to Non-Participating or from Non-Participating to Participating will need all the above forms AND the following form.
WEIM - Transfer - Resource Relinquishing Scheduling Coordinator - Letter Template

BSCID Scheduling Coordinator Templates
Energy Imbalance Market Scheduling Coordinator Request for BSCID
WEIM - Transfer - Resources Between BSCIDs - Same Scheduling Coordinator

Scheduling Coordinator Letter Guides
WEIM Relinquishing Scheduling Coordinator Letter Resource Guide
WEIM Resource Owner Scheduling Coordinator Letter Resource Guide
WEIM Scheduling Coordinator Acceptance Letter Resource Guide

Transmission customers of WEIM entities

Our computer based training modules are for Transmission Customers of WEIM Entities to learn about participation in the WEIM, the real-time market, base schedules, system outages, metering and settlements. For WEIM updates, subscribe to news releases and notices. Transmission customers should contact their WEIM entity for most questions. For all other questions, contact ISO customer service.

Governance and regulation

Business Practice Manuals
Business Practice Manuals contain implementation details through which the California ISO and market participants conduct business in accordance with the Tariff. The Business Practice Manual for Western Energy Imbalance Market contains information about all WEIM entity types.

Tariff
The Western Energy Imbalance Market is governed by the California ISO (ISO) FERC-approved Tariff. Each section or appendix of the tariff is maintained and updated independently according to effective dates of the FERC accepted tariff amendment.

Section 29 of the ISO Tariff addresses the provisions related to the Western Energy Imbalance Market. Appendix B. 17 – 20 contains agreements related to WEIM participation.

Regulatory filings and orders
All publicly available California ISO-authored filings and FERC orders are posted on the ISO website.

ISO Department of Market Monitoring
The ISO Department of Market Monitoring (DMM) keeps a close watch on the efficiency and competitiveness of the Western Energy Imbalance Market. Links to tariff provisions discussing DMM’s role and responsibilities and various DMM reports, presentations and tariff filings are available on the ISO website.