MenuWith Thanksgiving in the rear-view mirror, we are now starting the countdown clock to Christmas. In a few weeks, kids will be unwrapping presents and enjoying their gifts! For those of us that are following supply and demand balances carefully, we will have to wait a little longer to unwrap the “Capacity Christmas” present. But I don’t think we will be disappointed with the magnitude of capacity additions in the WECC.
The reason for the longer wait is the lag in reported capacity additions. That is, a monthly report from the Energy Information Administration (EIA) called the “Preliminary Monthly Electric Generator Inventory” or the EIA 860M contains important generator online information. These data are released near the end of the month and cover the prior month. For example, the October file was just released on November 25th. We expect the November release on December 23rd and the final release for 2025 to be towards the end of January.
The “Capacity Present” has shown up in December over the last few years. In fact, since 2018 the amount of capacity reported online in December has been greater than any other month with the exception of 2022 when March has 10 MW more capacity additions than December.
Figure 1 | Historical Monthly Capacity Additions by Fuel Type in the WECC as reported in the October 2025 EIA 860M.
The figure above shows the historical capacity additions in the U.S. portion of the WECC from 2018 to October 2025. Each bar represents the capacity additions and is colored by the fuel type of resource additions. We have previously reported that these additions are comprised of mostly to solar and storage additions, and mostly in California and the Desert Southwest. The figure above provides context for the monthly additions with December having large amounts of capacity showing up in the report. If the historical amounts of capacity in November and December hold true for 2025, we may have another record year.
Figure 2 | Historical Annual Capacity Additions by Fuel Type in the WECC as reported in the October 2025 EIA 860M.
The EIA 860M isn’t the only source of capacity additions available. There is plenty of information available through the resource Interconnection Queues and through Integrated Resource Plan (IRP). One of our recent efforts was to compile IRP capacity additions and load forecast data. The figure below shows this as planned capacity additions from Utility level IRPs across the WECC.
Figure 3 | Annual Capacity Additions by Fuel Type from Utility-level IRPs.
The figure above shows annual planned capacity additions by fuel type from a compilation of IRPs in the WECC. These data are either directly pulled from the IRP or linearly interpolated between two values within the IRP. Some noteworthy items from this analysis are the annual additions exceeding 12,000 MW per year which is consistent with a high amount of historical additions, a large amount of wind capacity additions which is inconsistent with the last few years of historical additions, and gas capacity additions which have been largely absent since 2020.
We use these data to help forecast future capacity, energy, and REC prices in the WECC with our long-term Production Cost Model (PCM). The PCM helps inform us of the capacity additions in the context of load growth and capital cost projections. The trend of increasing wind capacity additions is counter to much of our recent forecasts, however, could have important implications for price formation and asset valuation. If you are interested in learning more about our PCM capabilities, please contact us at [email protected] for more information.
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