Comments on Issue paper and stakeholder meeting discussion on June 4, 2026

1. Please provide a summary of your organization’s comments on the June 4, 2026 stakeholder meeting and the Issue Paper.

Idaho Power appreciates the June 4, 2026 stakeholder meeting and supports CAISO’s efforts, alongside DMM, to improve and add default VOM adders through more data-driven methodologies. We generally support approaches such as inflation-based updates and the use of market-informed data to maintain cost relevance.

However, greater transparency is needed regarding the underlying data, assumptions, and calculation methods. Idaho Power emphasizes that how datasets are selected and treated materially impacts outcomes, averages may be more appropriate for curated datasets (e.g., LTSA), while medians may better address variability in broader datasets (e.g., negotiated values).

2. Please provide any comments in support of or concerns for the proposed inflation-based update to the default VOM adders.

Idaho Power generally supports the proposed inflation-based update to the default VOM adders as a reasonable approach to maintaining cost relevance. However, additional transparency is needed regarding the underlying data, including recent negotiated VOM adders and the specific industry-wide cost study metrics used to inform the proposal.

Further clarification would also be beneficial around the characterization of certain values as “slightly more conservative” or “slightly higher” than the average of existing negotiated VOM adders. Quantifying these deviations, for example, whether they represent a 5% or 10% difference from the average, would improve stakeholders’ ability to understand and evaluate the methodology.

Additionally, it is unclear how the proposed values compare to the median of the referenced dataset, and what rationale CAISO used to position some values below the average and others above it. Greater insight into these decisions would enhance confidence in the approach.

While Idaho Power finds the use of inflation-based adjustments to be generally reasonable, it cannot fully assess the validity of the proposed VOM values without access to the supporting data and analytical metrics referenced in the paper. Furthermore, given that this process occurs on a three-year cycle, relying on historical data and projecting costs forward over the next three years, it may be reasonable to consider whether values should be anchored at or slightly above historical averages, recognizing the likelihood of continued inflation over the forecast horizon.

3. Please provide any comments in support of or concerns for the recommended option (LTSA-based median value) for establishing a default variable operations cost for storage resources? and Among the four proposed options for establishing default variable operations costs for storage resources (LTSA-based, negotiated values, manufacturer-based, or status quo), which option do you support and why?

Idaho Power supports the establishment of a default variable operations cost for storage resources and believes that Options 1 through 3 each have merit. We see viable paths to support any of these approaches. However, we do not support Option 4 (status quo), as it does not reflect current market conditions or improvements in available data.

Option 1 (LTSA-based approach):

Idaho Power agrees with the rationale that LTSA data is likely a more accurate representation of variable operating costs than PPA-based values, as it better reflects ongoing maintenance and service expectations. However, we do not support the use of the median value in this context. If LTSA data is considered the most robust and reliable dataset, further excluding high and low values diminishes its usefulness. By selecting LTSA as the sole dataset, a level of data filtering has already occurred, and additional exclusion through reliance on the median appears unnecessary. This narrowing of the data is evident when comparing averages across the provided tables for example, the LTSA average ($17.87) versus the Total/OEM average ($23.25). Accordingly, Idaho Power believes the average would be a more appropriate and representative measure than the median for this dataset.

Option 2 (Negotiated values):

It is reasonable to include negotiated VOM values from CAISO-verified and registered resources as part of the dataset. If these values have been reviewed and approved through the CAISO process, they should be considered valid data points. Excluding them raises concerns regarding consistency in data treatment. Given the broader variability and potentially project-specific nature of these values, Idaho Power agrees that using the median would be more appropriate when incorporating this expanded dataset, as it helps mitigate the influence of outliers.

Option 3 (Manufacturer-based approach):

Building on the assumption that all submitted and approved VOM data points are valid, it is reasonable to categorize the data by manufacturer (OEM) to better reflect technology-specific cost structures. Once grouped in this manner, Idaho Power again believes that the average value within each OEM category would provide a more consistent and representative measure than the median. Using the average in this context better captures the full range of observed costs within each manufacturer grouping.

4. Please provide any additional comments, feedback, or examples. You may upload supporting materials using the attachments field.

Idaho Power appreciates and supports the Variable Operations and Maintenance cost review conducted by CAISO and the Department of Market Monitoring (DMM). However, we do not agree with the assumption that “if the VOM values were too low, the ISO would be constantly negotiating VOM adders.”

In Idaho Power’s experience, all default VOM adders are below our actual VOM costs for comparable technology types. Historically, we have not pursued negotiated VOM adders or renegotiated VOM values for specific resources, not because the values were accurate, but because these costs are only relevant under market power mitigation, which occurs infrequently. As a result, the default values were considered sufficiently close for limited use cases.

That said, this dynamic is changing. Idaho Power is actively pursuing negotiated VOM adders for many of its resources, as the current default values no longer adequately cover actual operating costs. This shift suggests that for Idaho Power’s case, reliance on negotiation frequency alone is not a reliable indicator of whether default VOM values are appropriately calibrated.