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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.
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