20240202PAC to Staff 1-24.pdf

1407 W North Temple, Suite 330 Salt Lake City, Utah 84116
February 2, 2024
Ida Elmasian Utilities Administrative Assistant
Idaho Public Utilities Commission 11331 W. Chinden Blvd., Building 8, Suite 201-A P.O. Box 83720 Boise, Idaho 83720-0074
[e-mail]
RE: ID PAC-E-23-24 IPUC Set 1 (1-24)
Please find enclosed Rocky Mountain Power’s Responses to IPUC 1st Set Data Requests 1-24.
Provided via BOX are Attachments IPUC Audit 6-1 and 14-2. Confidential information is
provided subject to protection under IDAPA 31.01.01.067 and 31.01.01.233, the Idaho Public Utilities Commission’s Rules of Procedure No. 67 – Information Exempt from Public Review, and further subject to the non-disclosure agreement (NDA) executed in this proceeding.
If you have any questions, please feel free to call me at [phone].
Sincerely,
____/s/____
J.Ted WestonManager, Regulation
Enclosures
RECEIVEDFriday, February 2, 2024 11:52 AM
IDAHO PUBLIC
UTILITIES COMMISSION
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 1
IPUC Data Request 1 Please explain why the Company did not update integration charges based on the Flexible Reserve Study (FRS) in the 2021 Integrated Resource Plan (IRP), after
the acknowledgement of the IRP, as required by Order Nos. 33937 and 34966.
Response to IPUC Data Request 1
The Company is aware that Idaho Public Utilities Commission (IPUC) Order Nos.
33937 and 34966 ordered to the Company to continue to file “any future updates to its integration rates after the Commission has acknowledged its IRP supporting the update.” The Company understands that IPUC staff has interpreted this language that the Company is required to file an update to the integration charges subsequent to acknowledgement of every Integration Resource Plan (IRP). Based
on this foregoing, the Company responds as follows:
The Company acknowledges that it did not update the integration charges based on the Flexible Reserve Study (FRS) in PacifiCorp’s 2021 IRP, after the
acknowledgement by the Idaho Public Utilities Commission (IPUC) of
PacifiCorp’s 2021 IRP. While the Company does not have any records indicating why an update to the integration charges was not filed after acknowledgment of the 2021 IRP, going forward, the Company is willing to commit to updating the integration charges
after the acknowledgement of every IRP.
Recordholder: Mark Alder

Sponsor: Mark Alder
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 2
IPUC Data Request 2 Please provide examples of Non-Variable Energy Resources (Non-VER) resources and explain why they require regulation reserves.
Response to IPUC Data Request 2 Non-variable energy resources (VER) include all resources that are not wind or
solar, and which are not dispatchable. Some examples include run-of-river hydro
projects (such as generators on the North Umpqua and Bear River systems), cogeneration facilities (such as Kennecott, Tesoro and Exxon Mobil), as well as the Company’s Blundell geothermal facility and a small number of other generation types.
Regulation reserve requirements are calculated based on the difference between
forecasted output in the hour-ahead time frame, and actual output in each five-minute interval over the course of each hour. Relative to VER like wind and solar, non-VERs typically have less variation within the hour and smaller differences
between forecasted and actual output, but the variation and differences are not
zero and regulation reserves have to be available to compensate for those variations. Within PacifiCorp’s Flexible Reserve Study (FRS), the regulation reserve requirements account for the collective variation in load, wind, solar, and non-VERs and requirements are lower when changes in wind and solar are offsetting.

Dispatchable resources also have differences between forecasted and actual output, but this is because they actively respond to system dispatch signals and adjust their output to keep the system in balance. This system dispatch is
effectively the deployment of regulation reserves and does not add to the
regulation reserve requirement. Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 3
IPUC Data Request 3 Page 125 of the FRS states “While PacifiCorp had significant increases in both wind and solar capacity on its system in 2021, there has not yet been time to collect and
assess sufficient historical data that includes this expanded output. Therefore, for the
2023 IRP, PacifiCorp is continuing to use the methodology developed in its 2021 Flexible Reserve Study (FRS), which relied upon historical data from 2018-2019 ... Because the FRS methodology accounts for changes in PacifiCorp's resource mix,
both the quantity and cost of reserves has been updated for the 2023 IRP”.
Please respond to the following: (a) Please explain the impact, including the pros and cons, of using 2018-2019 data instead of using more recent data;

(b) Please explain if the Company would have made any changes in wind and solar forecasting and data collection methods had the Company used more recent data compared to the methods used during the 2018 and 2019 study period;

(c) Please explain the "changes in PacifiCorp's resource mix" that were used to update the quantity and cost of reserves for the 2023 IRP; and (d) Please explain how the resource mix was "accounted for".
Response to IPUC Data Request 3
Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), the Company responds as follows:

(a) For PacifiCorp’s 2023 IRP, generator deviation data (i.e. forecast errors) from the 2018-2019 historical period is scaled up to reflect the forecasted wind and solar capacity in PacifiCorp’s portfolio over time. This assumes that wind and solar resources have the same level of forecast errors as PacifiCorp’s existing fleet. While forecast errors in a single resource are likely to be higher than the
simultaneous errors across a fleet of resources, PacifiCorp already had substantial
quantities of wind and solar in 2018-2019. The forecast errors from an expanded fleet could be lower, as a result of diversity across an expanded pool of resources, or the errors could be higher, because the expanded pool of resources is in close proximity to existing resources and are likely to experience similar weather conditions at similar times. Absent analyzing the data, it is not possible to determine which result might prevail. Keeping in mind that several resources were added in the middle of 2021, when the 2023 IRP commenced during summer 2022, the available actual data was not of sufficient duration to warrant conducting the analysis. Any measurement could be a result of the shorter sampling period,
rather than a change in the underlying level of forecast errors.
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 3
(b) PacifiCorp’s contracts for short-term wind and solar forecasting from UL Solutions. These forecasts are used in actual operations and intra-hour deviations are measured against them. In general, the forecast provider continually works to
improve their product, particularly for new resources for which available history is
limited. However, while improvements could potentially occur, there have not been any specific modifications to the forecast methodology. Data on intra-hour deviations and actual output comes from energy imbalance market (EIM)
settlements, which also has not changed.
(c) The 2023 IRP preferred portfolio includes substantial increases in wind and solar capacity over time, as shown in the 2023 IRP, Volume I, Chapter 1 (Executive Summary), specifically Figure 1.3 (2023 IRP Preferred Portfolio New Solar Capacity) and Figure 1.4 (2023 IRP Preferred Portfolio New Wind Capacity).
These changes in wind and solar capacity were reflected in the quantity of reserves
required. Specifically, reserve requirements were calculated for the preferred portfolio of resources, then calculated again for the preferred portfolio plus a small increment of wind, and again for the preferred portfolio plus a small increment of
solar. For wind and solar, the change in reserve requirements in each hour of the
study horizon was calculated relative to the preferred portfolio, resulting in an hourly volume of additional reserve need for that quantity of resource. The integration costs also reflect the sources of available supply, and the integration costs presented in the 2023 IRP reflect the supply corresponding to the preferred portfolio, including proxy battery resources, which often provide reserves at little
or no cost, particularly if a large amount of storage capacity is available.
Specifically, the marginal regulation reserve cost is calculated by the PLEXOS model for each hour of the study horizon and can be reported for the short-term study results for the preferred portfolio. The hourly volume of reserve needed for
wind is multiplied by the hourly regulation reserve cost, and the result is divided
by the typical level of wind generation to yield a cost per megawatt-hour of wind output. A comparable calculation is prepared for solar. (d) Please refer to the Company’s response to subpart (c) above.
PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the
following website link: Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 4
IPUC Data Request 4 Please respond to the following regarding Table F.1 in the Application.
(a) Please explain whether "2018-2019 (2021 IRP)" should have been "2018-
2019 (2023 IRP)"; (b) Please explain whether 2,745 megawatts (MW) of wind capacity reflected the
wind capacity on the Company's system in the 2023 IRP; and
(c) Please explain whether 1,080 MW of solar capacity reflected the solar capacity on the Company's system in the 2023 IRP. Response to IPUC Data Request 4

Referencing the Company’s Application in this proceeding dated November 29, 2023, specifically Table F.1 (Portfolio Regulation Reserve Requirements), the Company responds as follows:

(a) Table F.1 refers to the historical data used in PacifiCorp’s Flexible Reserve Study (FRS) and identifies the first integrated resource plan (IRP) in which that historical data was presented. The values presented for 2018-2019 are not tied to a particular IRP and would not change if the label had been modified to refer to PacifiCorp’s 2023 IRP.

(b) The 2,745 megawatts (MW) of wind capacity in Table F.1 refers to the wind on PacifiCorp’s system in the 2018-2019 historical period, not to an amount during the 2023 IRP study horizon.

(c) The 1,080 MW of solar capacity in Table F.1 refers to the wind on PacifiCorp’s system in the 2018-2019 historical period, not to an amount during the 2023 IRP study horizon.
Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 5
IPUC Data Request 5 Table F.2 on Page 127 of FRS shows that the wind integration charge is $1.20/MWh and the solar integration charge is $1.48/MWh. However, Table F.2
on Page 6 of the Application shows that the wind integration charge is
$1.38/MWh and the solar integration charge is $1.59/MWh. Please reconcile these numbers.
Response to IPUC Data Request 5
Referencing the Company’s Application in this proceeding dated November 29, 2023, specifically Table F.2 (2023 FRS Flexible Resource Costs as Compared to 2019 Costs, $/MWh), the Company responds as follows:
Table F.2 in the Company’s Application accidentally reflected the values
identified in the PacifiCorp’s draft 2023 Integrated Resource Plan (IRP) dated March 31, 2023, and not the final 2023 IRP published on May 31, 2023. The difference is the result of slight changes in the preferred portfolio and the final
values of $1.20 per megawatt-hour ($/MWh) for wind and $1.48/MWh for solar
reflect the updated hourly modeling run prepared for the final 2023 IRP. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link:
Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil

Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 6
IPUC Data Request 6 Page 145-146 of the FRS states that, during the historical period, "portfolio diversity from the interactions between the various classes results in a regulation
reserve requirement that is 36% lower than the sum of the stand-alone
requirements, or approximately 679 MW." Please explain how the 36% and the 679 MW are determined and provide the workpapers showing the calculations with the formula intact.
Response to IPUC Data Request 6 Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), the Company responds as follows:
Please refer to Attachment IPUC 6-1 and Confidential Attachment IPUC 6-2
which provide details on the calculation of reserve requirements based on the deviations in the historical period. Specifically, please refer to Attachment IPUC 6-1, file “References Tables and Figures.xlsx”, tab “References”, cells C7 through
C9. The total requirement after accounting for portfolio diversity is 679
megawatts (MW) which is a 36 percent reduction from the 1,057 MW requirement in the absence of portfolio diversity. The requirement in the absence of portfolio diversity is the simple sum of the stand-alone reserve requirements individually calculated for load, wind, solar, and non-variable energy resources (VER). Diversity varies between PacifiCorp East (PACE) and PacifiCorp West
(PACW), by hour of the day, and by season. For example, it tends to be higher
during the middle of the day, when reserve requirements reflect variation in solar output. For details on the underlying calculation of diversity in the historical period, please refer to Attachment IPUC 6-1, folder “Calculations”, file “1.a.
Portfolio Diversity Benefit - Diversity Fractions.xlsx”.
PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link: Integrated Resource Plan (pacificorp.com)

Confidential information is provided subject to protection under IDAPA 31.01.01.067 and 31.01.01.233, the Idaho Public Utilities Commission’s Rules of Procedure No. 67 – Information Exempt from Public Review, and further subject to the non-disclosure agreement (NDA) executed in this proceeding.
Recordholder: Dan MacNeil Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 7
IPUC Data Request 7 Please respond to the following regarding Energy Imbalance Market (EIM) Diversity Benefits.

(a) Please list all types of reserves (e.g. regulation reserves, load following, etc.) that are reduced because of EIM Diversity Benefits; and
(b) If EIM Diversity Benefits represent reductions associated with other types of
reserves in addition to regulation reserves, please explain why all EIM Diversity Benefits, instead of portion of them were used in calculating integration charges. Response to IPUC Data Request 7

(a) PacifiCorp’s Flexible Reserve Study (FRS) categorizes regulation reserves as all of the reserve needs other than contingency reserve requirements. In the past, the Company has distinguished “regulating” requirements that require
fast-responses from “following” requirements that require a slower sustained
response, based on reliability standards applicable at the time to these different types of conditions. The current reliability standards do not make these distinctions therefore they are no longer part of the calculation, and a single type of reserve is identified. These reserves are also held collectively to cover all deviations in load, wind, solar, and non-variable energy resources
(VER), so there is no apportionment specifically to the individual categories,
though requirements as a whole are reduced. Energy imbalance market (EIM) diversity benefits reduce the need for this single type of reserve, though the total cannot fall below the floor set based on the California Independent
System Operator’s (CAISO) EIM uncertainty requirements, which is included
in the calculation. (b) Please refer to the Company’s response to subpart (a) above. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the
following website link:
Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 8
IPUC Data Request 8 Please respond to the following regarding Table F.4 (EIM Diversity Benefit Application Example) on Page 147 of FRS.

(a) Please explain how data in Column (a) through (d) were determined and whether the amounts were provided by EIM participants; and
(b) Please explain how data in Column (t) was determined. Response to IPUC Data Request 8 Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), Table F.4 (EIM Diversity Benefit Application Example), the
Company responds as follows:
(a) Reserve requirements in columns a through d are calculated by the California Independent System Operator (CAISO) as the energy imbalance market (EIM)
market operator, based on each balancing authority areas (BAA) recent historical
deviations in forecasted load and resources. These amounts are intended to ensure EIM participants provide sufficient resources to meet a range of potential conditions to prevent leaning and help ensure adequate capacity is available to meet market requirements, but it does not ensure that individual balancing authority areas meet their North American Electric Reliability Corporation (NERC) reliability
requirements. The referenced data is calculated by CAISO in accordance with EIM
business practices and is a percentile of a rolling sample of recent historical results. (b) The Company assumes that the reference to “Column (t)” was intended to reference
column (f). Based on the foregoing assumption, the Company responds as follows:
The referenced data is calculated by CAISO in accordance with EIM business practices, based on recent historical data on differences in forecasted and actual load and resources for the sum of all EIM participants in aggregate. Because load and resource deviations vary in timing among participants, aggregation results in a
smaller error at the same percentile level.
PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link: Integrated Resource Plan (pacificorp.com) Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 9
IPUC Data Request 9 Page 147 of the FRS states that "CAISO's published uncertainty requirements and associated diversity benefits are now only valid for March 2018 forward." Please
explain how the results are adjusted for January and February of 2018 to account
for EIM diversity benefits. Response to IPUC Data Request 9

Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), the Company responds as follows: The Company’s estimate of the energy imbalance market (EIM) diversity benefits varies seasonally and is based on the available data for March 2018 through
February 2019. Please refer to the Company’s response to IPUC Data Request 6,
specifically Attachment IPUC 6-1, file “_Portfolio Fit - EIM Support.xlsx” for details. The seasonal definition is provided below:
PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link:
Integrated Resource Plan (pacificorp.com) Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 10
IPUC Data Request 10 Page 147 of the FRS states that "EIM diversity benefits used in the FRS would have reduced regulation reserve requirements by approximately 140 MW." Please
explain how the 140 MW was determined and provide the workpapers that
calculate the amount with the formula intact. Response to IPUC Data Request 10

Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), the Company responds as follows: Please refer to the Company’s response to IPUC Data Request 6, specifically Attachment IPUC 6-1, file “_Portfolio Fit – EIM Support.xlsx”. The referenced
file contains the reserve requirements for the energy imbalance market (EIM) area
as a whole, and for the individual participants. The ratio of the requirement for the area as a whole to the sum of the participants’ individual requirements is the “diversity fraction”, i.e. the requirement after accounting for diversity. The
diversity credit (i.e. savings) is calculated by multiplying one minus the diversity
fraction by PacifiCorp’s individual east or west requirements. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link:
Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil

Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 11
IPUC Data Request 11 Table F.5 Page 147 of the FRS shows that regulation reserve drops from 1,057 average megawatts (aMW) to 540 aMW due to the portfolio diversity benefits and
the EIM diversity benefits. However, Page 146 states that the portfolio diversity
benefits are approximately 679 MW, and Page 147 states that the EIM diversity benefits are approximately 140 MW. These amounts will result in a regulation reserve amount of 238 MW, instead of 540 aMW. Please reconcile the amounts.
Response to IPUC Data Request 11 Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), Table F.5 (2018-2019 Results with Portfolio Diversity and EIM Diversity Benefits), the Company responds as follows:

The stand-alone requirement is 1,057 megawatts (MW) as shown in Table F.5. The requirement after accounting for portfolio diversity benefits is 679 MW, a reduction of approximately 36 percent as indicated on pages 145 and 146 of
PacifiCorp’s Flexible Reserve Study (FRS). The 140 MW reduction for energy
imbalance market (EIM) diversity benefits reduces the value to 540 MW after accounting for rounding. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link:

Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 12
IPUC Data Request 12 Please confirm that, in Table F.5 on Page 147 of the FRS, the data in Column "Stand-alone Regulation Forecast (aMW)" are calculated based on the 100% level
of the data in Column "Capacity (MW)", using the methodology shown in Figure
F.3 through Figure F.10. Response to IPUC Data Request 12

Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), Table F.5 (2018-2019 Results with Portfolio Diversity and EIM Diversity Benefits), the Company responds as follows: As indicated in Table F.5, capacity is listed at nameplate for resources and at the
12 coincident peak (CP) for load (the average of the highest loads in across the 12
months in the year). Figure F.3 through F.10 of PacifiCorp’s Flexible Reserve Study (FRS) identify the error on the y-axis as a function of the forecasted generation or load for a given hour divided by the nameplate capacity for
resources on the x-axis. Stated another way, the x-axis represents the forecasted
capacity factor (CF) for a resource type in a given hour. For example, Figure F.3 (Wind Regulation Reserve Requirements by Forecast – PACE) identifies that the maximum shortfall when PacifiCorp East (PACE) wind is forecasted at 10 percent of its nameplate is around 10 percent. The maximum shortfall when PACE wind is forecasted at 50 percent of its nameplate is around 35 percent. The
maximum shortfall when PACE wind is forecasted at 90 percent of its nameplate
is around 30 percent. The amount of installed wind resource on the system is unchanged across those three data points, rather than forecasted output of the wind fleet is varying.

Generally, the total nameplate of installed generation capacity is constant in the analysis for Figure F.3 through Figure F.10 of the FRS (other than minor changes for a small number of newly operational units, which are controlled for by analyzing the capacity factor of the resources then present on the system in each hour).

PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link: Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 13
IPUC Data Request 13 Page 149 of the FRS states that "the incremental regulation reserve analysis for the 2021 FRS methodology assumes that wind, solar, and load deviations scale
linearly with capacity increases from the actual data in the 2018-2019 historical
period." Please respond to the following: (a) Please explain why Non-VER deviations were not considered;

(b) Please provide an example to show how actual data in the 2018-2019 historical period were used in linearly scaling wind, solar, and load deviations; (c) Please explain if changes in PacifiCorp's resource mix from the 2023 IRP were considered in the scaling process;

(d) Please explain whether the purpose of the scaling process is to determine the standalone regulation reserve associated with each class (wind, solar, and load) in the incremental regulation reserve analysis; and

(e) If so, please explain whether the linear scaling depends on the pattern shown in the 2018-2019 historical data (i.e. Figure F.3-F.10). Response to IPUC Data Request 13
Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II,
Chapter F (Flexible Reserve Study), the Company responds as follows: (a) PacifiCorp does not anticipate significant changes in non-variable energy
resource (VER) nameplate capacity, keeping in mind that this does not include
dispatchable resources. Therefore PacifiCorp’s Flexible Reserve Study (FRS) methodology holds non-VER deviations constant at the historical level. (b) Please refer to the Company’s response to IPUC Data Request 6, specifically Confidential Attachment IPUC 6-2, which provides the requested calculations.
Column N and P of tabs “PACE” and “PACW” have the historical deviations,
while the annual adjustment factor corresponding to a specified level of load, wind, and solar is entered in cells T1 through V1. (c) The scaling process itself does not consider the 2023 IRP resource mix, as the scaling is only dependent on the selected wind and solar scaling factors. For example, in Table F.7 (PacifiCorp East Diversity by Portfolio Composition) of PacifiCorp’s FRS, the 100 percent level for wind and solar corresponds to the 2018-2019 actual wind and solar capacity and resulted in a 48 percent diversity benefit. When more wind and solar are added and wind and solar
deviations are scaled up proportionately, the diversity benefit drops. In
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 13
contrast, in Table F.8 (PacifiCorp West Diversity by Portfolio Composition) of PacifiCorp’s FRS, additions of solar result in additional diversity up to around the 500 percent solar capacity level, as solar was relatively low in the historical period, while increased wind capacity, which is already relatively
high, results in lower diversity. When applying these results to the 2023 IRP,
it is simply a matter of identifying where in Table F.7 and Table F.8 the wind and solar capacity in the portfolio would land after accounting for portfolio selections and any expired contracts.

(d) The purpose of the scaling process is not to determine the standalone regulation reserve requirement. The purpose of the scaling process is to repeat the portfolio diversity benefit analysis with the load and non-VERs deviations, but with wind and solar deviations that have been scaled to various levels of wind and solar additions. The errors as a function of forecasted energy levels
shown in Figure F.3 through Figure F.10 of PacifiCorp’s FRS, and the
resulting fitted quantile regression values continue to be used but are applied to a different quantity of wind and solar resource depending on the scaling. These quantile regression values are only dependent on the specific resource
or load stated, and do not have any portfolio diversity. After these stand-alone
values are calculated, the portfolio diversity credit reduces the total obligation. As wind and solar increase and become a larger driver of the total reserve need, their deviations are less likely to be offset by reserves that would otherwise have been required anyway to cover variations in load or non-VERs. Proportionately more reserves would be required in that situation and
the diversity benefit would go down.
(e) Yes. For example, the linear scaling assumes that a doubling of wind capacity would not impact Figure F.3 (Wind Regulation Reserve Requirements by
Forecast – PACE) of the FRS or F.4 (Wind Regulation Reserve Requirements
by Forecast Capacity Factor – PACW) of the FRS, both the largest errors as a function of capacity factor (CF) and the quantile regression that estimates those errors. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the
following website link:
Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 14
IPUC Data Request 14 Page 149 of the FRS states that "increases in PacifiCorp's portfolio capacity would result in a greater proportion of the EIM diversity benefits being allocated
to PacifiCorp." Please provide examples to illustrate how this was implemented. Response to IPUC Data Request 14
Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II,
Chapter F (Flexible Reserve Study), the Company responds as follows: Please refer to Confidential Attachment IPUC 14-1 which provides work papers that show the calculation of reserve requirements for the 2023 IRP preferred portfolio. Please refer to Attachment IPUC 14-2 which provides a copy of the
non-confidential work papers related to PacifiCorp’s 2023 IRP Appendix F
(Flexible Reserve Study). The energy imbalance market (EIM) diversity benefit is proportionately increased to account for changes in load, wind, and solar, relative to the historical levels during the period when the EIM diversity data was
collected. The calculation is primarily based on the change in wind and solar
nameplate capacity, but also accounts for the fact that changes in solar capacity have limited impact on diversity during hours without solar generation. Specifically, within each of the “Regulation Reserve Requirement 23IRP” templates provided in Confidential Attachment IPUC 14, please refer to tab “BAA Reserve Requirements”. The “Portfolio Requirement” (before EIM) is in
column Z, while the “Portfolio Requirement with EIM Adjustments” (after EIM
diversity is accounted for) is in column AB. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the
following website link:
Integrated Resource Plan (pacificorp.com) Confidential information is provided subject to protection under IDAPA 31.01.01.067 and 31.01.01.233, the Idaho Public Utilities Commission’s Rules of
Procedure No. 67 – Information Exempt from Public Review, and further subject
to the non-disclosure agreement (NDA) executed in this proceeding. Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 15
IPUC Data Request 15 Please respond to the following regarding Table F.6 on Page 150 of the FRS.
(a) Please provide justifications for the application of an exponent to the
incremental requirement more than the EIM minimum requirement to determine portfolio diversity;
(b) Please explain why /\75%, /\85%, and /\95% were reasonable levels to
calculate portfolio diversity; (c) Please explain which percentage was used in Table F. 7 and Table F. 8 and why;
(d) Please explain which percent was used in calculating the final integration
charges and why; and (e) Please explain the relationship between the data in Table F.6 and the data in
Table F.7. Response to IPUC Data Request 15 Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), Table F.6 (Portfolio Diversity Exponent
Example), the Company responds as follows:
(a) In general, greater diversity implies a greater overall requirement, with diversity among more elements. For example, when the sun is down at night,
the system is inherently less diverse, because one of the elements is absent –
there is no risk of shortfalls or of an exceedance driven by solar output when there is no solar output. Subtracting a uniform diversity benefit from all hours will overestimate the diversity at night. With that in mind, the exponent approach smooths out the forecasted reserve
requirement so that values approach but do not drop below the minimum and
so that diversity savings are prioritized toward hours when the megawatt requirement is high (and thus diversity is high). (b) Table F.6 of PacifiCorp’s FRS provides an example. The referenced levels in the FRS vary based on balancing authority area, season, and hour of the day, and were calculated to minimize overall regulation reserve requirements by ensuring that the diversity benefit did not exacerbate risks at either very high reserve requirements, or at very low reserve requirements (at or near the energy imbalance market (EIM) minimum requirement).

PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 15
(c) Please refer to the Company’s response to IPUC Data Request 6, specifically Confidential Attachment IPUC 6-2, confidential file “3. Loss of Load Probability - Dynamic Capacity Forecast CONF.xlsm”, which provides details on the calculation of the referenced values. The referenced file develops
coefficients specific to hour of the day and season which ensure sufficient
regulation reserves are held at different penetrations of wind and solar capacity.
(d) The diversity exponents vary by year with changes in PacifiCorp’s 2023 IRP
preferred portfolio. For example, in 2024, PacifiCorp East (PACE) has 3,234 megawatts (MW) of wind and 1,973 MW of solar, so the inputs are interpolated based on a weighted share of the following cases. Study 1 and Study 3 are weighted more heavily because the 3,234 MW wind nameplate is closer to 3,024 MW than to 4,064 MW. Study 1 is weighted slightly higher
than Study 3 because the 1,973 MW solar nameplate is only slightly closer to
1,462 MW than 2,502 MW:
Study East Wind East Solar
1 3,024 1,462 32.3% 38.5%
2 4,064 1,462 18.3% 32.9%
3 3,024 2,502 31.3% 37.1% 4 4,064 2,502 18.1% 33.8%
(e) Table F.6 of the FRS is an example of how diversity is forecasted and applied
– as a function of the magnitude of the requirements with smaller reductions when those requirements are low and larger reductions when requirements are high. Table F.7 (PacifiCorp East Diversity by Portfolio Composition) of the FRS identifies the results of the analysis, when the diversity forecasting technique is applied to the scaled historical deviation data at a variety of wind
and solar penetration levels, identifying the average degree by with reserve
requirements can be reduced from the stand-alone level. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the
following website link:
Integrated Resource Plan (pacificorp.com) Recordholder: Dan MacNeil

Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 16
IPUC Data Request 16 Page 149 of the FRS states that "the 2021 FRS methodology calculates the portfolio diversity benefits specific to a wide variety of wind and solar capacity
combinations ... " Please explain why only wind and solar are considered and why
load and NonVER are not. Response to IPUC Data Request 16

Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), the Company responds as follows: For the IRP analysis, load deviations are also scaled with changes in peak load across the IRP study horizon. With regard to non-variable energy resources
(VER), please refer to the Company’s response to IPUC Data Request 13.
PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link:

Integrated Resource Plan (pacificorp.com) Recordholder: Dan MacNeil
Sponsor: Dan MacNeil

PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 17
IPUC Data Request 17 Please respond to the following regarding Table F.7 on Page 150 of the FRS.
(a) Please explain what the percentages on the y-axis represent;
(b) Please explain the relationship between the Wind Capacity (MW) and the percentages (%) on the y-axis;

(c) On the y-axis, if 1,575 MW is 100%, please explain why 166% results in 3,024 MW; (d) Please explain what the percentages on the x-axis represent;
(e) Please explain the relationship between the Solar Capacity (MW) and the
percentages (%) on the x-axis; (f) On the x-axis, if 855 MW is 100%, please explain why 166% results in 1,462
MW;
(g) Please explain how percentage intervals are determined on the x-axis and the y axis; and (h) Please explain how the starting point of 788 MW for wind and the starting
point of 428 MW for solar are determined. Response to IPUC Data Request 17
Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II,
Chapter F (Flexible Reserve Study), the Company responds as follows: Please refer to the Company’s response to IPUC Data Request 6, specifically Attachment IPUC 6, file “References Tables and Figures.xlsx”, tab “Tables 3-4” which provides the data supporting what was labeled as Table F.7 (PacifiCorp
East Diversity by Portfolio Composition” in the Flexible Reserve Study (FRS).
(a) The percentages were intended to make it easier to see the change in wind capacity (y-axis) and solar capacity (x-axis), as a share of the values in the original study (100 percent for both wind and solar) but can be disregarded. A portion of the wind and solar resources in the PacifiCorp East (PACE) and PacifiCorp West (PACW) balancing authority areas (BAA) is owned by third-party transmission customers and not sold to PacifiCorp to serve its retail load obligations. As the BAA operator, PacifiCorp provides ancillary services to such customers under its Open Access Transmission Tariff (OATT), and that
obligation is incorporated in the FRS, however, for the portfolio composition
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 17
analysis presented in Table F.7, the wind and solar capacity associated with third party customers was not projected to expand in the same manner as that for PacifiCorp’s portfolio for its own customers. Where the percentage values exceed 100 percent, the divisor may reflect both PacifiCorp’s capacity (in the
“Wind Capacity (MW)” column, plus the aforementioned third-party capacity.
There may also be an error in the calculation. (b) Please refer to the Company’s response to subpart (a) above.

(c) Please refer to the Company’s response to subpart (a) above. (d) Please refer to the Company’s response to subpart (a) above. (e) Please refer to the Company’s response to subpart (a) above.

(f) Please refer to the Company’s response to subpart (a) above. (g) The portfolio diversity analysis produces diversity values over a wide range of
wind and solar penetration levels. The specific values merely represent data
points across the range and do not have any specific basis. (h) The starting point for the analysis was the 2018-2019 actual wind and solar levels, designated as 100 percent. To allow for possible retirements or contract expirations, the portfolio diversity analysis was also conducted down to half
of the 2018-2019 actual wind and solar, but not all of the possible
combinations were assessed. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the
following website link:
Integrated Resource Plan (pacificorp.com) Recordholder: Dan MacNeil

Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 18
IPUC Data Request 18 Page 149 of the FRS states that "a portfolio diversity value is calculated specific to each hour of the day in each season". Please respond to the following:

(a) Does each hour of each season have a Portfolio Composition (like the one shown in Table F. 7 and Table F. 8)?
(b) What hour and season does Table F. 7 represent?
(c) What hour and season does Table F. 8 represent? Response to IPUC Data Request 18
Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II,
Chapter F (Flexible Reserve Study), the Company responds as follows: (a) A single average portfolio composition is determined for each calendar year
within the IRP corresponds to the average portfolio composition over the
2018-2019 historical period. The portfolio composition is relatively uniform because resource additions in the IRP occur on January 1st. (b) Table F.7 (PacifiCorp East Diversity by Portfolio Composition) and Table F.8 (PacifiCorp West Diversity by Portfolio Composition) of PacifiCorp’s
Flexible Reserve Study (FRS) represent the change in average requirements
over the 2018-2019 historical period, at various levels of wind and solar capacity.
(c) Please refer to the Company’s response to subpart (b) above.
PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link: Integrated Resource Plan (pacificorp.com)

Recordholder: Dan MacNeil Sponsor: Dan MacNeil

PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 19
IPUC Data Request 19 Page 151 of the FRS provides an example where "the diversity exponent for hour five in the spring for a PACW study with 1,000 MW of wind and 1,000 MW of
solar would reflect a weighting of diversity exponents in hour five in the spring
from four scenarios." Please respond to the following: (a) Please define "diversity exponent" and explain how it is determined.
Specifically, does it refer to the "'75%, "'85%, and "'95% listed on Page 150 of
the FRS? (b) Please define "weighting of diversity exponents" and explain how it is determined. Specifically, does it refer to the percentages in Table F. 8 on Page 151 of the FRS?

(c) Does each combination of wind and solar have four scenarios? (d) Please list the weighting of each scenario that leads to a total of 100%.

(e) What is the ultimate portfolio diversity benefit for 1,000 MW of wind and 1,000 MW of solar? Please provide the workpaper that calculates it with the formula intact. Response to IPUC Data Request 19

Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), the Company responds as follows:
(a) Please refer to the Company’s response to IPUC Data Request 6, specifically
Confidential Attachment IPUC 6-2 which provides the work paper used to develop the diversity exponents. The results of the analysis are presented on tab “5” for the 0.5 hour per year loss of load probability (LOLP) level presented in the Flexible Reserve Study (FRS). The forecasted regulation reserve requirement specific to a specified level of wind and solar capacity is
calculated in column E of tabs “PACE” and “PACW”, and references
diversity values at the top of columns M through P on tabs “PACE Exceedance” and “PACW Exceedance”, respectively. A macro within the file is used to identify the lowest possible diversity exponents (i.e. lowest reserve requirements) during specific hours and seasons that still achieve the targeted level of reliability. (b) Underlying the portfolio diversity results presented in Table F.7 (PacifiCorp East Diversity by Portfolio Composition) and Table F.8 ((PacifiCorp West Diversity by Portfolio Composition) in the FRS are diversity exponent values
by east/west, season, and hour that are applicable to a specified level of wind
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 19
and solar capacity. These values are contained in the work paper referenced above. An example of the weighting using PacifiCorp West (PACW) capacity levels is provided in Attachment IPUC 6-1, on tab “References”. For values specific to the 2023 IRP, please refer to the “Regulation Reserve Requirement
23IRP” templates provided with the Company’s response to IPUC Data
Request 14, specifically Confidential Attachment IPUC 14, columns AH through AI on tab “Portfolio Diversity”. The template calculates reserve requirements for one year at a time and includes pasted results on tabs
“Summary” and “Results”. To show the results for different years, simply
modify the year in cell M3 of tab “Summary”. (c) Generally, yes, though it is technically possible the portfolio selection could be exactly equal to one of the available data points.
(d) Please refer to tab “Portfolio Diversity” as referenced in the Company’s
response to subpart (b) above. (e) The Company has not prepared the requested calculation, which would
depend on the megawatt (MW) amounts by east and west, plus details on
hourly wind and solar capacity factors, as well as forecasted load. Specifically these are input in the “Regulation Reserve Requirement 23IRP” templates referenced above, tab “BAA Reserve Requirements”, as follows: - column H: hourly load factor (hourly load divided by annual peak load)
- column I: wind capacity factor
- column J: solar capacity factor - column O: annual peak load - column P: wind nameplate capacity
- column Q: solar nameplate capacity
Based on those inputs, the calculation of results is reflected in: - column Y: Stand-alone requirement - column Z: Portfolio requirement
- column AB: Portfolio requirement with EIM adjustments
PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link: Integrated Resource Plan (pacificorp.com) Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 20
IPUC Data Request 20 Please respond to the following regarding the incremental regulation reserves based on the preferred portfolio.

(a) Please confirm that in the incremental regulation reserve analysis (where new wind and solar resources are selected as future resources), the final regulation reserves are calculated as the standalone regulation reserve minus portfolio
diversity benefits and EIM diversity benefits;
(b) If confirmed, please explain how the final regulation reserves are allocated to wind, solar, load, and Non-VERs; and (c) Please explain the roles of Wind Reserve Case and Solar Reserve Case in the
allocation process.
Response to IPUC Data Request 20
(a) Confirmed.
(b) There is no allocation to individual categories within the reserve calculation itself. For the purposes of calculating the integration charge, the reserve calculation was repeated with a 5 megawatt (MW) increase in wind capacity relative to PacifiCorp’s 2023 Integrated Resource Plan (IRP) preferred
portfolio, and again for a 5 MW increase in solar capacity. The wind
integration cost was calculated based on the change in reserve requirements between the 2023 IRP preferred portfolio and the study that included a slight increase in wind capacity, and an analogous calculation was prepared for
solar.
(c) 100 percent of the change in regulation reserve requirements in the wind reserve case, relative to the 2023 IRP preferred portfolio results, are attributed to wind. 100 percent of the change in regulation reserve requirements in the solar reserve case, relative to the 2023 IRP preferred portfolio results, are
attributed to solar.
PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link: Integrated Resource Plan (pacificorp.com) Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 21
IPUC Data Request 21 Page 152 of the FRS states that the Wind Reserve Case "recalculates the wind reserve requirement for a portfolio with 5 MW more wind resources starting in
the first year proxy resources are potentially available and extending to the end of
the IRP study horizon (2025-2042)." Please respond to the following: (a) Please explain step-by-step how the Wind Reserve Case recalculates the wind
reserve requirement;
(b) Please explain why the additional 5 MW of wind is added; (c) Please explain what "the first year proxy resources are potentially available" means;

(d) Does it mean the first deficit year? If so, please reconcile the year 2025 and the first deficit year of 2026 shown on Page 163 of the 2023 IRP; and
(e) Please explain why the FRS does not calculate integration charges before
2025 (i.e. 2024). Response to IPUC Data Request 21 Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II,
Chapter F (Flexible Reserve Study), the Company responds as follows:
(a) Please refer to the Company’s response to IPUC Data Request 14, specifically Confidential Attachment IPUC 14, file “Regulation Reserve Requirement
23IRP - East Template 02132023 v2 w5W CONF.xlsm”. This is a copy of the
2023 IRP preferred portfolio regulation reserve requirements, with the following changes used to develop the wind reserve requirement: 1. The wind nameplate capacity from the preferred portfolio in column P of tab “Source” was copied into column Y of that tab.

2. The values in column P were replaced with a formula, the hourly value in column Y plus 5. 3. No change was made to the hourly capacity factor values, implicitly the 5 megawatt (MW) wind resource addition is a composite with the same aggregate capacity factor as the 2023 IRP preferred portfolio (including existing/contracted resources). 4. The resulting revised reserve requirement calculation is in column AB of
tab “BAA Reserve Requirements”.
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 21
5. The macro within the file was run using keyboard shortcut “CTRL+SHIFT+A” to calculate hourly values for each year of the IRP study horizon and paste the resulting values on tab “Summary” and tab “Results”.

6. The steps above were carried about for wind in PacifiCorp East (PACE) and PacifiCorp West (PACW), as well as for solar in both areas.
(b) The intent of the wind integration cost calculation is to report the cost of
holding the additional regulation reserves for an additional quantity of wind capacity. This cost was calculated based on the change in the reserve requirements when wind capacity was increased by 5 MW relative to the 2023 IRP preferred portfolio.
(c) PacifiCorp’s 2023 IRP did not include any proxy generation resource options
that could come online prior to 2025. In general, it can take two years or more to contract for, construct, and bring online a wind or solar resource, and longer for some other resource types.

(d) No, this does not refer to the deficit year. (e) The 2023 IRP does not include all of the short-term resources and market transactions used to balance the system in actual operations. As a result, it was not able to produce representative integration costs for earlier years.

PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link:
Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 22
IPUC Data Request 22 Please describe how integration charges are determined for IRP based avoided cost rates and explain whether the assumptions used in the IRP method match the
assumptions used in this case for published avoided cost rates. If not, what are the
differences? Response to IPUC Data Request 22

The Company applies the same Idaho Public Utilities Commission (IPUC) approved integration rates used in published avoided cost rates under the IRP-based avoided cost methodology.
Recordholder: Dan MacNeil
Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 23
IPUC Data Request 23 Please provide the data used to estimate the quantile regression model referenced on page 139 of the FRS. Please provide in Microsoft Excel format with formulae
intact and enabled. In addition, please provide the following:
(a) Copies of the quantile regression results for model(s) the Company estimated for its FRS and identify the Company's preferred model if more than one
model was estimated. Results should include statistics and diagnostics
applicable to quantile regression and coefficient estimates with associated standard errors, t-statistics, p-values, and confidence intervals; (b) An explanation on how regulation reserve requirements are co-optimized in the quantile regression model;

(c) Descriptions of all variables used in the regression modeling; (d) Regression coefficients used to define the functions for the classes: "Load
Error," "Wind Error," "Solar Error," and "Non-VER Error;" and
(e) Rationale for using linear effects on the predictor variable in determining "Load Error" (Page 140 of FRS). Response to IPUC Data Request 23

Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II, Chapter F (Flexible Reserve Study), the Company responds as follows:
(a) The referenced analysis was conducted in the R statistical package.
(b) Regulation reserve requirements are calculated based on a single variable for each class (wind/solar/load/non-variable energy resources (VER)), as indicated by the designation on the x-axis in Figure F.3- through Figure F.10 of the Flexible Reserve Study (FRS). There is no co-optimization within the
regressions.
(c) Please refer to the Company’s response to subpart (b) above. (d) Please refer to the Company’s response to IPUC Data Request 14, specifically Confidential Attachment IPUC 14, the “Regulation Reserve Requirement 23IRP templates” files, tab “Coefficients”. (e) While it may not be readily apparent from Figure F.9 (Reserve Requirements (Average MW)) and Figure F.10 (Flexible Resource Supply Forecast
(Average MW)), the sample size for load factors in excess of 90 percent is
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 23
significantly lower than that for more moderate load levels. The absence of measured errors at high load factors is thus at least in part attributable to having fewer measurements. Over the bulk of the load samples, the linear trend is a better predictor. Note: both wind and solar can both have weather
conditions that would allow for generation in excess of their nameplate. For
example, once wind reaches its maximum output, additional increases in wind speed does not increase output, but they do reduce the likelihood of variations that drop wind speed to a level when generation is impacted. Similarly for
solar, output in excess of inverter capacity reduces the likelihood that changes
in insolation will impact generation levels. These effects are represented in the wind and solar predictions. Keep in mind that when the aggregate area-wide capacity factors used in this analysis are relatively high, some portion of the wind and solar fleet is likely already at 100 percent output and subject to reduced variation in generation output, even if a portion of the fleet is not.

PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the following website link:
Integrated Resource Plan (pacificorp.com)
Recordholder: Dan MacNeil Sponsor: Dan MacNeil
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 24
IPUC Data Request 24 Please provide the work papers associated with Table F.5 as referenced in Page 147 of FRS and explain how each entry in the table was derived or calculated.
Please provide the data in Microsoft Excel format with the formula intact.
Response to IPUC Data Request 24
Referencing PacifiCorp’s 2023 Integrated Resource Plan (IRP), Volume II,
Chapter F (Flexible Reserve Study), the Company responds as follows: Please refer to the Company’s response to IPUC Data Request 6, specifically Attachment IPUC 6-1, including the file “References Tables and Figures.xlsx” and other files linked to that file.

The referenced table includes the following columns: - “Stand-alone Regulation Forecast (aMW)”: Regulation reserve requirements
for each class, sufficient to meet reliability obligations in the absence of any
reserves or deviations from other classes. - :Stand-alone Rate (%)”: the Stand-alone Regulation Forecast value for each class, divided by its capacity.
- “Portfolio Regulation Forecast w/EIM (aMW)”: the hourly regulation reserve
requirement is reduced as a result of portfolio diversity and energy imbalance market (EIM). This percentage reduction is applied to each class based on their stand-alone requirements for that hour. The resulting reduction for solar
is slightly higher than for other classes, because in hours when solar is
present, portfolio diversity tends to be slightly higher than when it is not present. - “Portfolio Rate (%)”: the Portfolio Regulation Forecast value for each class, divided by its capacity.

- “Capacity (MW)”: the amount of resources and load in the study. - “Rate Determinant”: Whether “Capacity” refers to nameplate capacity (in the case of generating resources) or the average of the 12 monthly coincident peaks (CP), applicable to load. Note: while these results are representative of the historical period for the Flexible Reserve Study (FRS) and the relative contribution of different classes to the overall requirements, the sub-allocation of requirements among resources and
load is not used in the 2023 IRP, where models a single reserve requirement for
PAC-E-23-24 / Rocky Mountain Power February 2, 2024 IPUC Data Request 24
PacifiCorp East (PACE) and one for PacifiCorp West (PACW), based on overall requirements. PacifiCorp’s 2023 IRP is publicly available and can be accessed by utilizing the
following website link:
Integrated Resource Plan (pacificorp.com)

Recordholder: Dan MacNeil Sponsor: Dan MacNeil
1
Joe Dallas (ISB #10330) 825 NE Multnomah, Suite 2000 Portland, OR 97232 Telephone No. [phone]
Email: [e-mail] Attorney for Rocky Mountain Power
BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION
MATTER OF THE APPLICATION
IZATION TO UPDATE THE WIND

-E-23-24

I, Joe Dallas, represent Rocky Mountain Power in the above captioned matter. I am a
senior attorney for Rocky Mountain Power.
I make this certification and claim of confidentiality regarding the response to the attached
Idaho Public Utilities Commission Staff discovery request pursuant to IDAPA 31.01.01 because
Rocky Mountain Power, through its response, is disclosing certain information that is Confidential
and/or constitutes Trade Secrets as defined by Idaho Code Section 74-101, et seq. and 48-801 and
protected under IDAPA 31.01.01.067 and 31.01.01.233. Specifically, Rocky Mountain Power
asserts that information contained within the Company’s response IPUC Data Request No. 6 and
14 contain Company proprietary information that could be used to its commercial disadvantage.
Rocky Mountain Power herein asserts that the aforementioned responses contain
confidential in that the information contains Company proprietary information.
2
I am of the opinion that this information is “Confidential,” as defined by Idaho Code
Section 74-101, et seq. and 48-801, and should therefore be protected from public inspection,
examination and copying, and should be utilized only in accordance with the terms of the
Protective Agreement in this proceeding.

DATED this 2nd day of February, 2024.

Respectfully submitted,

By__________________________
Joe Dallas Senior Attorney Rocky Mountain Power