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Key Differences Between WEIS & WEIM

November 14, 2024
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Disclaimer: This blog post answering “What are the key differences between WEIS and WEIM?” was generated using PCI’s ISO/RTO Documentation AI Chatbot, powered by ChatGPT. While the content is based on curated market documentation, it is intended for informational purposes only and may not reflect the most up-to-date or comprehensive information. We recommend verifying any key details directly with relevant sources before making business decisions. 

For the latest answer to this question, generated live, visit our free ISO/RTO Documentation Chatbot.

 

 

The Western Energy Imbalance Service (WEIS) and the Western Energy Imbalance Market (WEIM) are both real-time energy markets designed to balance supply and demand, but they have some key differences in their structure, operation, and scope. Here are the main distinctions: 

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Western Energy Imbalance Service (WEIS) 

  • Operator: The WEIS Market is operated and administered by the Southwest Power Pool (SPP). 
  • Market scope: WEIS focuses on providing a real-time Energy Imbalance Service within the Western Interconnection. It simplifies the energy imbalance process by focusing on economic bids, ancillary service plans, commitment plans, and non-conforming load forecasts. 
  • Market participation: WEIS includes Market Participants who participate in a price-based real-time Energy Imbalance Service. It does not require pre-hour base schedule submissions, making the process less complex. 
  • Market monitoring: The Market Monitor for WEIS assesses the design and structure of the WEIS Market to ensure market efficiency and compliance with market rules. It does not monitor bilateral energy, transmission, or capacity markets unless they affect the WEIS Market. 
  • Future changes: WEIS is set to be replaced by SPP’s next market iteration, such as Markets+ or RTO West, once they are operational. 

Western Energy Imbalance Market (WEIM) 

  • Operator: The WEIM is operated by the California Independent System Operator (CAISO). 
  • Market scope: WEIM is a broader regional market that includes multiple entities across the Western Interconnection. It leverages resource diversity across several Western states and enables energy transfers between balancing areas. 
  • Market participation: In WEIM, resources within a Balancing Authority Area (BAA) can elect to be participating or non-participating. Participating resources execute a participating resource agreement and are represented in the market by a scheduling coordinator. 
  • Market benefits: Since its inception in 2014, WEIM has grown to include numerous participating entities and has produced significant financial benefits for its participants. It has generated more than $2 billion in gross economic benefits and significantly reduced renewable energy curtailments by routing excess production to other regions. 
  • Precision and accuracy: WEIM offers real-time visibility into surrounding electric grids and an improved ability to balance fluctuations in supply and demand, making it highly precise and accurate. 

Summary of key differences 

  • Operator: WEIS is operated by SPP, while WEIM is operated by CAISO. 
  • Market scope: WEIS focuses on real-time energy imbalance within the Western Interconnection, whereas WEIM has a broader regional scope with multiple participating entities. 
  • Market participation: WEIS involves Market Participants in the Western Real-Time Balancing Market (WRTBM), while WEIM allows resources to choose between participating and non-participating status. 
  • Market monitoring: WEIS has specific market monitoring protocols that do not extend to bilateral markets unless they affect the WEIS Market, while WEIM’s monitoring is integrated within CAISO’s broader market oversight. 


These differences highlight the distinct operational and structural characteristics of the WEIS and WEIM markets.
 

For more detailed insights, you can read the following blog posts: 

  • A Look Ahead: The Future of the West Markets 
  • What Is the ‘SPP Market’ and What Does It Do? 
  • What Is CAISO? Understanding California’s Energy Market Operator 


For the latest updates and more information, visit our
ISO/RTO Documentation Chatbot. 

 

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The ISO/RTO Documentation AI Chatbot (ISO AI) is a specialized AI tool designed to provide accurate and detailed information about the operations, procedures and regulations of U.S.-based Independent System Operators (ISOs) and Regional Transmission Organizations (RTOs) based on their business practice manuals (BPMs). It will enable you to quickly build expertise in markets including CAISO, ERCOT, ISO-NE, MISO, NYISO, PJM, and SPP (including WEIS), and familiarize yourself with new markets like SPP Markets+ and EDAM, while offering quick access to the resources the chatbot’s answers are based on so that you can verify the information independently or explore topics in greater depth.

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