Skip Ribbon Commands
Skip to main content

The Generation Resource Adequacy Forecast Webpage


The Generation Resource Adequacy Forecast (GRAF) replaces the Power Supply Assessment (PSA). The GRAF is a detailed, interactive environment for you to explore the many levels of resource adequacy (RA) in the Western Interconnection. The GRAF shows both the deterministic and probabilistic parts of resource adequacy assessments to give you a better understanding of potential risks in the interconnection. As the growth of variable resources expanded the resource portfolio, the results of deterministic resource adequacy became outdated and the PSA became less valuable. Users were simply extracting data for their own modeling and ignoring the results published from WECC modeling. To stay relevant, the report needed to highlight the probabilistic results of resource adequacy. Unfortunately, results from probabilistic modeling are very large compared to deterministic results. Presenting all the layers of the results without producing thousands of pages became an issue. Using Microsoft’s Power BI visualization tool, WECC was able to show the results of the probabilistic RA work in a useful way.

How to use this report

We have divided the tool into sections you can access in the menu on the left. We further divided each section into pages for each topic. You can jump between pages using the menu on the left or the buttons at the bottom of each page. However, the report is designed to be read through from start to finish the first time you use it. The Road Map section on each page explains how each part of the resource adequacy is studied. Each section builds upon the previous sections. Once read through, the "Exploring Resource Adequacy" page brings all the charts together so you can study all the sections at once.

Interacting with Charts and Maps

Click a region in the map and watch as the graphics update to show the corresponding data. Some charts offer a view of data by hour, year, or month. Click the corresponding options to see specific data.


Demand in the Western Interconnection is projected to grow from about 906 GWh in 2020 to around 972 GWh in 2029—just over a 7% increase. The combined peak hour demand for all regions in the Western Interconnection is in the summer and is expected to grow from about 162 GW in 2020 to over 176 GW in 2029, an increase of almost 9%.

The expected nameplate capacity installed is about 258 GW in 2020, growing to 275 GW in 2029; about 6.5% growth. The expected portfolio mix in 2020 is 51% baseload, 29% hydro, 11% wind, and 10% solar.

The annual weighted margin is expected to be around 66% in 2020, slightly declining to 63% by 2029. The monthly weighted margin varies between 85% in the spring to just under 50% in the summer.

The overall annual weighted threshold margin for the Western Interconnection is about 16%. The threshold in the spring months is closer to 20%; it drops to 14% in the summer months.

Most of the hours in which the expected margin falls below the threshold margin occur in the summer months. All hours experience some risk; with hours 18 and 19, which immediately follow the evening peak demand, seeing the highest risk.

Transfers are available for most hours in which the expected margin falls below the threshold margin. Therefore, all areas can alleviate risk in the system through transfers except for a few hours in the CAMX area beginning in 2020 and growing over the next 10 years.