Washington’s Ecology Department has clarified that state cap-and-invest rules that apply to CAISO’s Western Energy Imbalance Market also will cover the ISO’s Extended Day-Ahead Market (EDAM) when it begins operations in 2026.
An agency guidance document released Sept. 3 explains how the cap-and-invest program attributes an appropriate volume of greenhouse gas emissions to energy imported into Washington via a centralized electricity market (CEM). The WEIM is the only centralized market operating in the West, with SPP’s Markets+ expected to go live in 2027.
The GHG attribution process is complicated by the difficulty of pinpointing exactly what resource in a centralized market produced the energy imported into the state to meet a market participant’s demand.
Under existing rules, energy transferred into Washington via the WEIM is classified as an “unspecified import” and assigned a default emissions factor of 0.428 MT CO2e/MWh. The rules require that the Washington-based load-serving entity or market participant receiving the import be responsible for reporting the emissions to the Ecology Department.
But a 2024 law (SB 6058) prompted Ecology last December to adopt a new framework that will allow the agency to trace the origin and emissions factor of CEM energy transfers into Washington — transfers that will be categorized as “specified imports” with specific associated emissions rates.
To do that, the new framework calls for centralized market operators such as CAISO and SPP to establish a system for identifying a “deemed market importer” for transfers into Washington, defined as “the market participant that successfully offers electricity from a resource or system into a CEM, which then is “attributed to Washington by the methods put in place by the market operator of that CEM.” The deemed market importer also will be the entity responsible for reporting emissions to the agency.
The Sept. 3 guidance notes that existing reporting rules will remain in place through 2026, but it advises market operators to put a “specified imports” system in place by Jan. 1, 2027.
It also clarifies that although the rules were written with the real-time WEIM in mind, they also apply to EDAM.
“Ecology notes that all optimization of electricity supply from market resources and attribution of imported electricity to Washington through the day-ahead market, EDAM, ultimately occurs in real-time, within the WEIM,” the agency wrote. “For this reason, Ecology clarifies that provisions applicable to the ‘energy imbalance market’ within WAC 173-441-124(3)(v), apply equally to entities participating in WEIM and EDAM.”
