Council reviews needs assessment results based on simulating Northwest power system in 2031

In recent years, the Pacific Northwest power system has experienced strains during peak demand periods in the wintertime during storms, and in the summer months during heatwaves. Residents need energy to use space heating to stay warm when temperatures plunge, and air conditioning to stay cool when extreme heat blankets the region. Two examples have been during the June 2021 heat dome and the January 2024 polar vortex event.

These were tests of the Northwest power supply's resource adequacy. An adequate power supply means the grid can provide the energy needed to meet all the demands that are placed on it. Under the Northwest Power Act, one of the Council's core power planning responsibilities is to protect the regional electricity grid's resource adequacy.

While the regional power system was able to successfully navigate both the 2021 heat dome and the 2024 polar vortex without resorting to emergency firm load-shedding, also referred to as rolling blackouts, they were major resource adequacy tests. Extreme events like winter storms and summer heatwaves are also extending multiple days, which is a trend expected to grow in years to come based on climate modeling scenarios for the Northwest.

The Council's Ninth Power Plan will include a cost-effective resource strategy that will solve these and other future energy demand challenges. The Council expects to have a draft of the Ninth Plan ready for public review and comment by mid-2026. This strategy will ensure that the Pacific Northwest continues to enjoy an adequate, efficient, economical, and reliable power supply.

At October's Council meeting in Donnelly, Idaho, Power Division staff presented results of a new needs assessment that examines a simulation of the Northwest power system in 2031 under intentionally limited circumstances (read presentation | watch video).

A needs assessment compares the capabilities of the existing power grid in the Northwest against forecasted energy demand. It does not include a resource strategy for addressing the resulting gap; that will be developed in the Council's power planning processes in the remaining months of 2025 and the winter and spring months of 2026. The needs assessment is different from the Council's annual adequacy assessments, which test its power plans' resource strategies.

To easily grasp the premise of the Council's needs assessment, imagine if the Pacific Northwest's energy demands continued growing until 2031, the regional transmission system added several new projects and expanded its capacity, and the Western Interconnection continued to develop new generating resources. Except, the Pacific Northwest stopped building generating resources in 2025, and stopped acquiring demand-side resources like energy efficiency and demand response products. What would be the size of the gap that the region would need to solve to ensure an adequate power supply by 2031? That's the question the Council's needs assessment sought to answer.

At the October meeting, Power Planning Director Jennifer Light provided an overview of the needs assessment results. The key takeaways are:

• The modeling shows significant needs for the region in 2031
• Needs are seen across all seasons, but the largest and longest gaps appear in the winter
• The expected load growth is the largest driver of the needs seen in this study
• Peak challenges are greater than energy challenges, meaning that a portfolio of supply- and demand-side resources will be needed to meet both peak and energy needs identified in these studies throughout the year

One of the primary factors for the size of the power system's needs in 2031 is the Council's new 20-year load forecast for the Northwest, which Power Division staff published in April. When it published the load forecast in the spring, the Council urged the public to exercise caution in interpreting the results, because they show higher peaks and annual energy demand than will actually occur.

This is because this load forecast is a frozen-efficiency forecast - meaning it intentionally doesn't account for the cost-effective energy efficiency, demand response, and rooftop solar that will be identified through the plan analysis and be included in the Ninth Plan's resource strategy. These resources flatten peaks and reduce electricity demand.

For example, unmanaged electric-vehicle charging that often occurs in after-work hours can coincide with other peak hour power needs. Demand response programs could manage the charging in several different ways that have less impact on power system peaks - such as after midnight. The initial load forecast assumes unmanaged charging, leaving the demand response potential of managed charging as an option for Power Division staff's computer models to choose when they analyze different resource strategies for building out the Northwest electricity grid in the future.

How the needs assessment analysis was set up

The first component is the expected load growth for 2031. The Council's power planners created a suite of five different load pathways across three different climate futures (so 15 total). This helps to account for future uncertainty in economic conditions, or the pace of electrification of buildings and transportation, and data center development in the Pacific Northwest. This suite of forecasts covers low, medium, and high trajectories for future demand growth.

Load forecast trajectories - The following graphs show the forecast ranges for annual energy demand between 2027-2046, which is represented in average megawatts.

And, here is the forecast's range for peak demands in the Northwest over the next two decades.

For the needs assessment, Council power planners used the mixed bag pathway, which is near a midpoint trajectory in the forecast range. This was because one of the needs assessment's goals is to help calculate an adequacy reserve margin. This margin helps to maintain an adequate power supply by ensuring enough backup power is available to cover unplanned events or periods of peak demand on the grid. It's calculated as a percentage of the forecasted peak demand. The percentages for the mixed bag pathway are intended to be scalable to other trajectories in the load forecast.

The next component is assessing the capabilities of the existing regional power system. For the existing system, Council power planners assume that includes all the grid's existing resources as well as any owner-announced unit conversions. That would include coal plants that are being converted to natural gas, for example.

Utilities' resource planning - Utilities in the Northwest have major resource additions planned for 2031 and beyond. In July, the Council received a presentation from the Pacific Northwest Utilities Conference Committee about these plans. The Council's study only included new projects that are currently under construction. The Council did not assume any other planned resources, including planned demand-side resources.

Columbia Basin hydrosystem - Power Division staff also modeled several different potential operations of the Columbia Basin hydrosystem, which is the largest generating resource on the Northwest's electricity grid. At August's Council meeting, staff explained each sensitivity of possible hydrosystem operations, the current uncertainty that exists about operations in 2026 and beyond, and how they proposed to navigate it.

Transmission - For the transmission system capabilities, Council power planners are assuming an expansion to the regional system by 2031. In addition to projects that are under construction today, like the Boardman-to-Hemingway line between Oregon and Idaho, staff included five projects that align with the Western Transmission Expansion Coalition's 10-year study. WestTEC is currently analyzing additional transmission projects on a 20-year timespan.

These five projects are the Cross Cascades North line, which will expand capacity between eastern Washington with the Puget Sound region, and Cross Cascades South, which will do the same for eastern Oregon and the Portland metro area. It also includes upgrades to the Path 8 line between Montana, northern Idaho, and eastern Washington, as well as a segment of the Gateway West project that will run east-to-west across southern Idaho. Finally, the needs assessment included the North Plains Connector that will run into Montana from the Dakotas.

Wholesale power markets - The final piece of this puzzle is future resource development in the Western Interconnection, which can offer a critically important supply of energy and capacity to meet electricity demand in the Pacific Northwest. This summer, Council power planners developed a new market study specifically for the needs assessment. One key point to understand is that the Council has worked with the region to set limits on market imports during peak demand periods, which helps to keep power system costs lower. Unexpectedly having to buy large quantities of electricity on spot markets in the West can be expensive, and the resources may not be available if the whole West is tight. The import limits are 2,500 MW in fall and winter, and 1,250 MW in spring and summer.

Needs assessment results

By running dozens of simulations of the Northwest power system throughout the year 2031, the analysis showed the regional electricity grid will require significant amounts of new supply and demand side resources to keep pace with the mixed-bag pathway's expected load growth. This result is expected given the Council's forecasted load growth.

The simulation operated a deeply inadequate power system in the Northwest in 2031, but 90% of the simulated shortfall events lasted one hour, and 93% were less than 1,250 MW. The needs assessment found the longest and largest challenges in wintertime, although peak challenges occurred throughout the year.

"There's a real peak problem in the system," Power Planning Director Jennifer Light told the Council. "That peak need is big, and that is one of the pieces that we're going to have to solve for. It's not just one resource that's going to solve this. That's why we keep emphasizing the point of a portfolio (of supply and demand side resources). There will be a portfolio that, working together, will meet those needs."

In fall 2025 and winter 2026, the Council's power planners will be using computer modeling to test various resource strategies to find cost-effective options that satisfy future energy demands while meeting resource adequacy thresholds and other system requirements. The resource strategy must meet the Northwest Power Act's legal mandate of assuring the four-state region of Washington, Idaho, Oregon, and Montana of an adequate, efficient, economical, and reliable power supply.

The Council welcomes and invites public engagement, input, and feedback from across the Northwest in its upcoming decision-making processes for the Ninth Power Plan.