In mid-March, Americans across the West experienced a major heat dome, with temperatures 10 to 30 degrees warmer than average and consistently over 100 degrees Fahrenheit.
It was the latest extreme weather event to challenge grid operators. A key tool during these times is the ability to import and export power via a market, as access to the largest set of resources gives operators the best chance to keep the lights on. And make no mistake. Heat waves like that are going to become a more frequent occurrence as the effects of climate change unfold.
Earlier in March, Arizona Corporation Commission Chair Nick Myers claimed that organizations like the Environmental Defense Fund (EDF) were advocating for regional electricity market choices that help California maintain control of the western power markets to benefit the state’s own policy priorities.
This is simply not the case. Groups like EDF advocate for outcomes based on which options, including regional electricity markets, provide the greatest benefits to ratepayers and the environment.
Case in point: recent analysis conducted by Aurora Energy Research and released by EDF showed that Arizona ratepayers could save more than $114 million per year between 2027 and 2040 by joining the Extended Day-Ahead Market (EDAM) as compared to joining SPP’s Markets+. None of that analysis focused on California. (See APS Would See Greater Savings in EDAM, Analysis Finds.)
Electricity market choice is complex and there are many factors that should be considered, but we believe the question of which market saves customers the most money should be at the center of any such decision.
Reliance Across the West
Events like the recent heat dome underscore why electricity markets matter. It’s not just California. States across the West are reliant on one another to keep electricity reliable and affordable. That’s why the size and configuration of day-ahead markets in the West will greatly impact electricity bills and grid reliability for decades to come.
Since 2014, Arizona ratepayers have saved nearly $1 billion via its participation in the Western Energy Imbalance Market. As utilities and regulators weigh joining the two major day-ahead markets, Extended Day-Ahead Market (administered by the newly formed Regional Organization for Western Energy) or Markets+ (administered by SPP), they should consider the full consequences of the decision.
The configuration of Western markets — and which market individual utilities ultimately join — will have enormous consequences for customers because seams between the two markets are not trivial. While they exist currently between different balancing authorities, the implications of future seams in the West, including the seam that will surround states like Arizona, are much more significant going forward than under the status quo — with greater financial and reliability consequences. This interdependence is precisely why the conversation around regional market development, and the choice of market like that in Arizona, matters so much.
For example, during Winter Storm Fern in January, real-time prices in PJM consistently hovered in the $250-$500/MWh range, with day-ahead prices spiking to over $2,000/MWh. Meanwhile, real-time prices on the other side of the seam in MISO were negative for nearly two consecutive days, hitting as low as -$315/MWh in the Chicago area. This enormous inefficiency caused by a market seam underlines the fact that transmitting electrons between markets adds costs. Without a course correction, Arizona utilities are on a path to essentially island the state.
Households across the West, especially those in Arizona, already are struggling to pay their electric bill. Arizona Public Service (APS) has asked the Arizona Corporation Commission for a rate increase of 14% by the end of 2026, while Tucson Electric Power (TEP) has sought roughly the same increase for its customer base.
Both utilities have committed to joining Markets+. Arizona Attorney General Kris Mayes is intervening in both proceedings over concern that the requested rate increase would result in too high of a burden on consumers.
Accurate and Timely Information
APS, TEP and the Salt River Project have argued that they see substantial benefits to joining Markets+ over EDAM, but the modeling they reference is outdated and the utilities have not provided transparent information on the underlying assumptions. This decision is important and it should be driven by accurate and timely information.
The Aurora analysis contracted by EDF is one of the only independent market choice studies conducted to date that evaluates the implications of the decision on Arizona’s utilities. It’s worth emphasizing that the focus of EDF’s analysis wasn’t California, but the impact of utility market decisions on Arizona.
The topline takeaway of the analysis is straightforward: the bigger the market, the bigger the savings. The analysis also shows that distributional effects of market benefits can vary by utility (modest system cost increase for one utility, along with larger statewide savings), which is another reason why these decisions require more regulatory scrutiny.
Families across the West are grappling with high electricity bills and whether they can afford to run their AC during an extreme heat event. Coordination through a regional market can ease these pressures, but as the Aurora analysis shows, not all markets provide equal benefits.
Utilities and their regulators should consider how these benefits compare across market options, and in places like Arizona, more work is needed to show their choices are in the best interest of their customers.
Alex DeGolia is director of state legislative and regulatory affairs and Michael Bueno is senior manager of state climate policy and strategy at the Environmental Defense Fund.




