20260401Application.pdf

HIQAW POWER.
MEGAN GOICOECHEA ALLEN
Corporate Counsel RECEIVED
mqoicoecheaallen(a)idahopower.com APRIL 1, 2026
IDAHO PUBLIC
UTILITIES COMMISSION
April 1, 2026
Commission Secretary
Idaho Public Utilities Commission
11331 W. Chinden Boulevard
Building 8, Suite 201-A
Boise, Idaho 83714
Re: Case No. IPC-E-26-08
Idaho Power Company's Application for its Annual Update to Marginal Pricing
Used in Certain Schedules
Dear Commission Secretary:
Attached for electronic filing, please find Idaho Power Company's Application in
the above-entitled matter.
If you have any questions about the attached documents, please do not hesitate
to contact me.
Sincerely,
Ay�r T
I f9CC�1.2.a �
Megan Goicoechea Allen
MGA:cd
Attachments
1221 W. Idaho St(83702)
P.O. Box 70
Boise, ID 83707

MEGAN GOICOECHEA ALLEN (ISB No. 7623)
DONOVAN WALKER (ISB No. 5921)
Idaho Power Company
1221 West Idaho Street (83702)
P.O. Box 70
Boise, Idaho 83707
Telephone: [phone]
Facsimile: [phone]
mgoicoecheaallenCa�,idahopower.com
dwalkerCa-)_idahopower.com
Attorneys for Idaho Power Company
BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION
IN THE MATTER OF IDAHO POWER )
COMPANY'S APPLICATION FOR ITS ) CASE NO. IPC-E-26-08
ANNUAL UPDATE TO MARGINAL )
PRICING USED IN CERTAIN ) APPLICATION
SCHEDULES )
Idaho Power Company ("Idaho Power" or "Company"), pursuant to Idaho Code §
§ 61-502 and 503 and Idaho Public Utilities Commission's ("Commission") Rule of
Procedure ("RP") 52, as well as relevant orders of the Commission including Order Nos.
35929 and 36619, submits this Application to initiate the Commission's annual review of
the marginal cost-based energy prices contained in Schedule 20, Speculative High-
Density Load ("Schedule 20") and Schedule 34, Lamb Weston Special Contract
("Schedule 34"), and further, to request that the Commission authorize the Company to
maintain the currently effective marginal cost-based energy prices in Schedule 20, and
APPLICATION - 1

Schedule 34, as a mitigation measure for the reasons explained herein.
In further support of this Application, Idaho Power represents as follows:
I. BACKGROUND
Case No. IPC-E-21-37- Schedule 20, Speculative High-Density Load
1. On November 4, 2021, Idaho Power filed Case No. IPC-E-21-37 seeking
authority to establish a new schedule to serve speculative high-density customers,
Schedule 20, Speculative High-Density Load.' In its application, the Company explained
that the rates included in Schedule 20 incorporate certain modifications to the existing
rate design for Schedule 9 and Schedule 19, including a proposal to price energy at a
marginal cost in all pricing periods, based on Avoided Cost Averages ("ACA") as
contained in Technical Report Appendix C of the Company's Integrated Resource Plan
("IRP").2 In its comments, Commission Staff ("Staff") noted that, while it agreed in
principle with using a marginal energy rate under the circumstances, it was concerned
with using an IRP-derived avoided cost in customer rates.3 Accordingly, Staff
recommended that the Company be authorized to rely on ACA from the Company's
Integrated Resource Plan as the initial basis for the cost of marginal energy in the
proposed Schedule 20, but that it be directed to evaluate that method against other
methods, "including a marginal energy cost rate derived from a test year in preparation of
the next general rate case."4
' In the Matter of the Application of Idaho Power Company for Authority to Establish a New Schedule to
Serve Speculative High-Density Load Customers, Case No. IPC-E-21-37, Application (Nov. 4, 2021).
2 Id. at 14-15.
3 Id., Staff Comments at 6 (Apr. 12, 2022).
4 Id.
APPLICATION - 2

2. On June 15, 2022, the Commission issued Order No. 35428 approving
Schedule 20 as filed and ordering the Company, in pertinent part, "to evaluate and
compare other methods for determining a marginal cost of energy in addition to the use
of ACA in the IRP for setting the Schedule 20 energy rate" before its next general rate
case.5
3. As directed by the Commission, the Company collaborated with Staff
following its evaluation, meeting with Staff on January 20, 2023, and again on February
2, 2023, to discuss the results of Idaho Power's evaluation and to solicit Staff's feedback.
Following these two discussions, Staff provided a memo ("Staff Memo"), which is included
as Attachment No. 1 to this Application, that memorializes the discussions between the
Company and Staff regarding the basis for marginal pricing of energy and outlines five
general criteria that should be considered when developing marginal cost-based
customer energy rates:
(i) The resources used in a model for determining marginal cost
should be based on the resources that are highly likely to exist
during the rate period.
(ii) The amount of incremental load used to determine the
marginal cost rate should reflect the amount of incremental
load for the portion of load that will be priced at marginal cost.
(iii) The marginal cost rates should have enough granularity to
reflect time difference (e.g., seasonality, time of day) value of
Marginal Cost within the Company's system to provide
accurate price signals.
(iv) If the marginal cost rates are based on a forecast, due to the
lack of marginal costs being trued-up in the PCA, they should
be updated often enough that they reflect current conditions or
find a way to true up the marginal cost to actual marginal cost.
5 Id., Order No. 35428 at 7 (Jun. 15, 2022).
APPLICATION - 3

(v) If market costs are used, cost of transmission transaction and
wheeling costs should be included.
Case No. IPC-E-23-18 - Lamb Weston Special Contract
4. Around the same time it was engaged in discussions with Staff regarding
marginal cost-based pricing methods, the Company had been exchanging information
and negotiating the terms, conditions, and rates with an existing retail customer, Lamb
Weston, relative to a new Special Contract ("Lamb Weston Special Contract")
necessitated by the customer expanding its operations to include new manufacturing
lines, raw and cold storage, and ancillary facilities.
5. After the parties reached agreement on the terms and conditions of the
Lamb Weston Special Contract, Idaho Power filed Case No. IPC-E-23-18 on May 23,
2023, requesting Commission approval of the same.6 In its application the Company
explained that it was proposing a two-block pricing structure, which contemplated an
embedded-cost pricing block, Block 1, and a marginal energy cost pricing block, Block 2.
6. The Company's proposed "Block 2 Energy Charge" was based on the per
kilowatt-hour ("kWh") marginal cost of energy based on the simulated hourly operation of
the Company's power supply system over expected hydro conditions.' Under this
method, net power supply expenses are first quantified using the Company's expected
load for the test year, then an incremental load increase is added to determine the
resulting increase in power supply expenses and generation. The difference in power
supply expenses between the initial and subsequent simulation is divided by the
6 In the Matter of Idaho Power Company's Application for Approval of Special Contract and Tariff
Schedule 34 to Provide Electric Service to Lamb Weston, Inc., Case No. IPC-E-23-18, Application (May
23, 2023).
Id. at 7.
APPLICATION - 4

incremental generation to produce a marginal cost per kWh.
7. The Company's proposed method for determining the marginal cost of
energy in the Lamb Weston Special Contract was consistent with those principles
identified by Staff as best practices that should be considered when evaluating marginal
pricing methodologies as set forth in the Staff Memo.
8. In the application, the Company further explained that to ensure the
marginal energy price applied to Lamb Weston's Block 2 energy usage keeps pace with
conditions experienced on the Company's system, the pricing should be updated
annually. More specifically, the Company proposed to submit an annual update to the
marginal energy price that would be filed around the time of the Company's annual Power
Cost Adjustment ("PCA") filing, with the updated marginal energy price proposed to be
effective June 1, consistent with PCA rates.$
9. On September 21, 2023, the Commission issued Order No. 35929
approving the Lamb Weston Special Contract and proposed pricing methodologies,
including the proposed marginal price method for the Block 2 Energy Charge and the
annual update to the marginal energy prices to be effective June 15c
Case No. IPC-E-23-11 — 2023 General Rate Case
10. On June 1, 2023, Idaho Power filed its application in Case No. IPC-E-23-11
('2023 GRU), requesting authority to increase its rates and charges for electric service.9
As part of its case, the Company proposed changes to Schedule 20 rates to reflect the
principles contained within the Staff Memo including the Company-proposed updating of
8 Id. at 10.
9 In the Matter of the Application of Idaho Power Company for Authority to Increase its Rates and
Charges for Electric Service in the State of Idaho and for Associated Regulatory Treatment, Case No.
IPC-E-23-11, Application (June 1, 2023).
APPLICATION - 5

the marginal energy component basis of Schedule 20 and aligning to the time-of-use
periods with those proposed for Schedules 9 and 19.10 More specifically, the Company
proposed replacing the current ACA-based marginal rates with an AURORA-based
method to be updated annually on June 1 using a forward test year consisting of the 12-
month period April through the subsequent March, consistent with spring power cost
filings.11
11. As part of the 2023 GRC, the Company also described its rate design
proposals for the Company's existing special contract customers, which sought to move
the rate design components toward class cost-of-service ("CCOS") informed amounts
when increasing forecast collections to recover the revenue requirement. This includes
reestablishing or updating the contract demand charge based on the same methodology
the Company recently employed for pending special contract customers, which at that
time included Lamb Weston. The Company explained that the marginal energy cost
portion of Lamb Weston's two-block pricing structure is based on an annual power supply
cost forecast consistent with the PCA test year, with proposed marginal cost rate updates
to occur at an annual interval in the spring with updated effective marginal energy rate
each June 1st
12. The parties agreed to resolve and settle all the issues in the 2023 GRC
following a series of settlement discussions, and as a result, on October 27, 2023, the
Company filed a Motion for Approval of a Stipulation and Settlement ("Settlement
Stipulation"). With respect to CCOS, the Settlement Stipulation provided that the parties
did not agree on any particular cost-of-service methodology and specified that it was not
10 Id., Goralski Direct Testimony at 50-51.
11 Id. at 52-53.
APPLICATION - 6

requesting that the Commission approve a particular CCOS methodology.12 It further
stated, however, that the Company's filed CCOS methodology, updated to reflect the
settled revenue requirement, was utilized on a limited basis to update certain rates,
including special contract rates, which included rates contained within the Schedule 34,
Lamb Weston Special Contract, that had been approved by the Commission effective
September 21, 2023.13
13. On December 28, 2023, the Commission issued Order No. 36042 approving
the Settlement Stipulation and authorizing the Company to implement its revised tariff
schedule with the terms of the Settlement, effective January 1, 2024. Thereafter, the
Commission issued Order No. 36067, approving the Company's compliance filings.
Case No. IPC-E-24-15 — Annual Update to Marginal Pricinq Used in Certain
Schedules
14. On April 1, 2024, the Company filed its application in Case No. IPC-E-24-
15 requesting to update the marginal cost-based energy prices contained in Schedule 20
and Schedule 34. The Company requested to update the marginal energy price
component for these schedules effective June 1, 2024. Consistent with the Commission-
approved methodology, the marginal cost of energy was determined by simulating the
hourly operation of the Company's power supply system under expected resources,
streamflow conditions, and fuel prices for the April 2024 through March 2025 test year.
First, base case net power supply expenses were quantified, then the model was rerun
with an additional 15 megawatts ("MW") of load. The difference in power supply expenses
between the base and the base-plus-15 MW scenario was divided by the difference in
12 Id., Stipulation and Settlement at 9 (Oct. 27, 2023).
13 Case No. IPC-E-23-18, Order No. 35959 (Oct. 13, 2023).
APPLICATION - 7

megawatt-hours to calculate the marginal cost of energy ("Two Run Method"). The 15
MW incremental load used in the base-plus-15 MW scenario was based on Lamb
Weston's expected incremental load. The same 15 MW basis was proposed for Schedule
20 because the Company did not have any Schedule 20 customers, and the Company
believed 15 MW represented a reasonable proxy until the Company had Schedule 20
customers taking or projected to take service. The Company also noted that it planned to
continue its investigation of methodologies for calculating marginal cost-based rates for
current and future customers and would engage with Staff to determine the best
method(s) moving forward.
15. On May 31 , 2024, the Commission issued Order No. 36201 approving the
Company's request to update the marginal energy price component of Schedule 20 and
Schedule 34, to be effective June 1, 2024.
Case No. IPC-E-25-17 — Annual Update to Marginal Pricinq Used in Certain
Schedules
16. Subsequently, Idaho Power held follow up discussions with Staff to review
the Two Run Method and explore potential refinements to the methodology. More
specifically, Idaho Power identified that the introduction of battery resources into the
model caused inaccurate and unintuitive marginal cost prices at the hourly level, as each
scenario run dispatched the batteries differently. As a result of the evaluation and
discussions with Staff, Idaho Power identified an improvement to its marginal cost of
energy methodology, which as more fully described herein, is referred to as the Single
Run Method.14
14 Specifically, criteria (iii) of the Staff Memo envisions an appropriate methodology will produce rates with
"enough granularity to reflect time difference (e.g., seasonality, time of day) value of Marginal Cost within
the Company's system to provide accurate price signals."
APPLICATION - 8

17. On April 1 , 2025, the Company filed its application in Case No. IPC-E-25-
17 requesting to update the marginal cost-based energy prices contained in Schedule 20
and Schedule 34. In the application, Idaho Power sought to apply the Two Run Method
for use in Schedule 34 because the Lamb Weston Special Contract prescribes use of that
methodology. However, Idaho Power recommended the Single Run Method for use in the
updated Schedule 20 pricing, as the results of the Two Run Method did not provide
accuracy at the hourly level.
18. The Single Run Method, like the Two Run Method, relies on an hourly
simulation of the Company's power supply system using expected resources, streamflow
conditions, and fuel prices for the test year, based on the most current information
available at the time of the filing. However, rather than comparing outcomes across two
scenarios, the Single Run Method identifies the marginal resource in each hour as
determined by the AURORA model and uses that resource to establish the hourly
marginal price. The hourly load input to the simulation is based on total system load,
excluding load priced at marginal cost, with an additional 100 megawatts included.
Depending on the total amount of load proposed to be priced at marginal cost in the test
year, multiple simulations may be performed in 100 MW increments. The results of these
simulations are then used to calculate a weighted-average marginal cost-based rate.
19. On May 30, 2025, the Commission issued Order No. 36619 approving the
Company's request to update the marginal energy price component of Schedule 20 using
the Single Run Method and Schedule 34 using the Two Run Method, effective June 1,
2025.
20. The Commission further ordered that the Company work with Staff to
APPLICATION - 9

evaluate methods to verify the current marginal cost forecasting methods against the
Company's actual marginal costs prior to the next annual update.
Case No. IPC-E-24-44— Micron FAB Special Contract
21. On December 6, 2024, Idaho Power filed an application seeking approval
of an Energy Services Agreement ("ESA") and Tariff Schedule 28 to provide electric
service to Micron Semiconductor Manufacturing ("Micron FAB").15 In that application, the
Company proposed to initially price Micron's energy on a marginal cost basis using the
single-run method, with the initial rate based on the 2024-2025 Power Cost Adjustment
("PCA") test year, which reflected expectations from April 2024 through March 2025. As
the Micron FAB case progressed, Idaho Power subsequently requested the Commission
approve the energy charge as set forth in the proposed Schedule 28, adjusted to reflect
the Commission-approved marginal cost-based pricing from Case No. IPC-E-25-17,
which was in effect for other customers subject to that methodology effective June 1,
2025.16
22. During that proceeding, concerns were raised regarding Idaho Power's
Commission-approved methodology for developing marginal cost-based energy charges,
including by the Idaho Irrigation Pumper's Association ("IIPA"). In testimony, IIPA's expert
witness raised concerns that the costs of Power Purchase Agreements ("PPAs"), referred
to in that docket as long run marginal energy costs, are not accounted for in Idaho Power's
current methodology because they are treated as "sunk costs" within the AURORA
15 In the Matter of Idaho Power Company's Application for Approval of Special Contract and Tariff
Schedule 28 to Provide Electric Service to Micron Idaho Semiconductor Manufacturing(Triton) LLC, Case
No. IPC-E-24-44, Application (December 6, 2024) and Supplement and Errata to Application (April 30,
2025).
16 Order No. 36619 issued in Case No. IPC-E-25-17 approved the annual rate of$40.84 per MWh, to be
effective June 1, 2025, through May 31, 2026.
APPLICATION - 10

model." In testimony filed in that case, Idaho Power acknowledged that the existing
methodology does not explicitly recover the cost of incremental PPAs. As a result, Idaho
Power proposed that the Commission direct an evaluation of these issues in a separate
marginal cost docket, filed independent of the annual update, to allow for a more
transparent and more appropriately scoped review of potential modifications.'$
23. As of the date of this filing, the Commission has not yet issued an order in
the Micron FAB ESA case, however, if the Commission approves the Company's request
as filed, Micron's Schedule 28 energy charge would be $0.04084 per kWh.
II. COMPLIANCE WITH ORDER NO. 36619
24. Consistent with the Commission's directive in Order No. 36619 issued in
IPC-E-25-17, Idaho Power met with Commission Staff on January 7, 2026, to discuss
potential approaches for evaluating the reasonableness of the Company's marginal cost
forecasting methods relative to actual system conditions. As a result of those discussions,
Idaho Power committed to including, with its filing, marginal cost proxies to compare
forecasted and actual outcomes. Consistent with that commitment, the Company has
completed this evaluation for the rates effective June 1, 2025, which is provided
separately in Attachment 2 to this Application.
III. REQUEST IN THIS PROCEEDING
25. The Company makes the instant filing in compliance with Commission
Order No. 35929 approving the annual update to marginal cost-based energy rates. As
part of this compliance filing, the Company has quantified marginal cost-based energy
prices based on the Two Run Method and the Single Run Method, the results of which
17 IPC-E-24-44. Kaufman Direct Testimony at 6-9.
18 IPC-E-24-44. Anderson Surrebuttal Testimony at 12-14.
APPLICATION - 11

can be found in Attachment 3 to this Application.
26. The Two Run Method. Consistent with the approach approved by the
Commission in Case Nos. IPC-E-23-18 and IPC-E-25-17, the Company applied the Two
Run Method by simulating a base case and a second AURORA run that includes an
incremental 15 MW of load. The marginal cost rate is then calculated as the difference in
total system costs between the two simulations, expressed on a per-MWh basis.
27. The Single Run Method. Consistent with the Commission-approved
methodology, the Company applied the Single Run Method by performing a single
AURORA simulation for the test year using the Company's expected system load, net of
load priced under the Single Run Method, plus an incremental 100 MW. Currently,
Schedule 28 (Micron FAB) is the only load incorporated in the Single Run Method,19 as
there are no customers taking service under Schedule 20.
28. In reviewing the results of the Commission-approved methodologies, Idaho
Power observed that the marginal cost-based energy rates produced under both methods
are lower than the embedded power supply cost rates forecast for the 2026-2027 PCA
test year. That is, absent mitigation, customers subject to marginal cost-based energy
rates will pay, on average, less than the embedded energy rates paid by other customers
through the PCA. Because marginal cost-based energy rates are intended to reflect the
incremental power supply costs incurred to serve applicable customer load and
19 While Case No. IPC-E-24-44 remains pending, generally, in that case Staff has recommended that the
Commission approve the Company's proposal to rely on the outcome of the annual marginal cost update
docket to inform the marginal cost-based energy charge for the Micron FAB. As noted in its December 16,
2025, Post-Hearing Brief in that docket, Idaho Power agreed with Staff's recommendation in this regard
and proposed that the Commission direct it to submit a compliance filing setting the initial Energy Charge
in Schedule 28 to $0.04084 per kWh consistent with the approved single-run rate from IPC-E-25-17.
Given the Company's proposal in this case for the Commission to maintain the currently in-effect marginal
energy price components, there would be no impact on the Company's recommendation in the Micron
FAB case to align the Energy Charge with the pricing approved in IPC-E-25-17.
APPLICATION - 12

considering the concerns raised regarding the treatment of long run marginal energy
costs, including PPAs, rates that fall below embedded power supply costs may not fully
recover those intended incremental costs.
29. Importantly, these issues were identified in the Micron FAB proceeding and
are expected to be addressed in a separate docket pending Commission direction in IPC-
E-24-44. Given that these issues have been identified but have not yet been addressed
by the Commission, Idaho Power believes it is appropriate to recommend mitigation in
this case and accordingly, requests the Commission direct it to maintain the currently in-
effect marginal cost-based energy rates for Schedules 20 and 34.
30. In the alternative, should the Commission instead determine that Schedules
20 and 34 be updated with the marginal cost-based energy rates consistent with the
approved methodology and consistent with Attachment 3, the Company will submit
revised tariff sheets reflecting such rates in a subsequent compliance filing.
IV. MODIFIED PROCEDURE
31. Idaho Power believes that a hearing is not necessary to consider the issues
presented herein and respectfully requests that this Application be processed under
Modified Procedure, i.e., by written submissions rather than by hearing. RP 201, et seq.
If, however, the Commission determines that a technical hearing is required, the
Company stands ready to prepare and present testimony in support of this Application in
such hearing.
APPLICATION - 13

V. COMMUNICATIONS AND SERVICE OF PLEADINGS
32. Communications and service of pleadings, exhibits, orders, and other
documents relating to this proceeding should be served on the following:
Megan Goicoechea Allen Grant T. Anderson
Donovan Walker Austen Apperson
IPC Dockets Jessi Brady
1221 West Idaho Street (83702) 1221 West Idaho Street (83702)
P.O. Box 70 P.O. Box 70
Boise, ID 83707 Boise, ID 83707
mgoicoecheaallen(a-),idahopower.com qandersonC@.idahopower.com
dwalker _idahopower.com aapperson(c)_idahopower.com
dockets(@Jdahopower.com jbradyidahopower.com
VI. REQUEST FOR RELIEF
33. The methods underlying the Company's analysis of updated marginal cost-
based customer energy rates in this case are consistent with those previously approved
by the Commission. However, due to the results produced by the application of the
approved methodologies, the updated marginal cost-based component of the energy
charges may not align with the intended purpose of the rates. Accordingly, Idaho Power
respectfully requests that the Commission issue an order: (1) acknowledging that the
updated marginal cost calculations provided in this filing and contained in Attachment 3
were correctly quantified, (2) finding that the Company complied with Order No. 36619 by
meeting with Commission Staff in advance of this filing, and (3) authorizing the Company
to maintain the currently in-effect marginal energy price components of Schedules 20 and
34.
DATED at Boise, Idaho, this 1 St day of April 2026.
,_/�T i c�ecln�an
MEGAN GOICOECHEA ALLEN
Attorney for Idaho Power Company
APPLICATION - 14

CERTIFICATE OF SERVICE
I HEREBY CERTIFY that on the 1st day of April, 2026 1 served a true and correct
copy of IDAHO POWER COMPANY'S APPLICATION upon the following named parties
by the method indicated below, and addressed to the following:
Commission Secretary Hand Delivered
Idaho Public Utilities Commission U.S. Mail
11331 W. Chinden Blvd., Bldg No. 8 Overnight Mail
Suite 201-A (83714) FAX
PO Box 83720 FTP Site
Boise, ID 83720-0074 X Email
C9 ���
Christy Davenport
Legal Administrative Assistant
APPLICATION - 15

BEFORE THE
IDAHO PUBLIC UTILITIES COMMISSION
CASE NO. IPC-E-26-08
IDAHO POWER COMPANY
ATTACHMENT 1

Mem arandum
Date: 2/16/2023
From : Yao Yin, Utilities Analyst, Idaho Public Utilities Com mssion
To: Connie Aschenbrenner, Idaho Power Com lany
Subject: Investigation in Methods to determ he Marginal Cost of Energy for Schedule 20.
Background
Order No. 35428 directed Idaho Power to evaluate and com lire other m dhods for
determ ping a in aginal cost of energy in addition to the use of Avoided Cost Averages in the
Integrated Resource Plan for setting the Schedule 20 energy rate,before the next general rate
case is developed and filed.
On January 31, 2013, Idaho Power in d with Staff and discussed potential in dhods for
determ ping m aginal cost of energy for the Schedule 20 energy rate and possibly for other
custom ars using in aginal cost of energy for their energy rates. As a result of the in(eting, Staff
agreed to develop som ecriteria for the Com piny to consider for developing a in dhod.
Criteria
Although this list in ay not be exhaustive, Staff identified the following criteria that could
be used for determ ping the final in dhod:
• T he resources used in a in odel for determ ring m aginal cost should be based on the
resources that are highly likely to exist during the rate period.
• T he am cunt of increm aital load used to determ he the in aginal cost rate should reflect
the am cunt of increm altal load for the portion of load that will be priced at in aginal cost.
• T he in aginal cost rates should have enough granularity to reflect tim edifference (e.g.
seasonality,tim eof day) value of Marginal Cost within the Com pany's system to provide
accurate price signals.
• I f the in aginal cost rates are based on a forecast, due to the lack of Marginal Costs being
trued-up in the PCA, they should be updated often enough that they reflect current
conditions or find a way to true up the m aginal cost to actual m aginal cost.
• I f market costs are used, cost of transm ssion transaction and wheeling costs should be
included.

BEFORE THE
IDAHO PUBLIC UTILITIES COMMISSION
CASE NO. IPC-E-26-08
IDAHO POWER COMPANY
ATTACHMENT 2

Forecast Proxy Marginal Cost Rates
7Day,Ahre Mid Hourly ELAP Gas Dispatch AURORA
Two Run Single Run s Prices Rate Backcast
$42.64 $40.84 5.68 $29551 $33.761 $30.86
Day-Ahead Mid-C Price
Time Period:Apr 1,2025-Mar 25,2026
Mid-Columbia(Mid-C)day-ahead prices represent a widely used regional benchmarkfor wholesale electricity prices in the Pacific Northwest and reflect market-clearing conditions for energy traded one day in advance.
Day-ahead prices reflect the cost of securing energy to meet anticipated load obligations prior to real-time system operations and incorporate unit commitment decisions,forecast uncertainty,and forward-looking risk.
Limitation:Represents a regional market outcome and may not reflect the Company's specific system conditions or modeled dispatch.
Hourly Energy Load Aggregation Point("ELAP")Price
Time Period.,Apr 1,2025-Mar 24,2026
ELAP prices reflect real-time balancing costs in the Western Energy Imbalance Market,where participants are generally expected to be balanced based on prior scheduling.
As such,ELAP prices represent the marginal cost of incremental deviations rather than full energy procurement.
Limitation:Reflects real-time balancing conditions rather than full system marginal cost.
Actual Gas Dispatch Rate
Time Period.,Jan 1-Dec 31,2025
Weighted-average gas dispatch rate based on actual gas costs in 2025.
Limitation:Gas-fired resources may not represent the marginal resource in all time periods.
AURORA Backcast
Time Period.,Jan 1-Dec 31,2025
AURORA backcast prices are produced by re-running the AURORA model using historical inputs(e.g.,actual gas prices,hydro conditions,and load)instead of forecast assumptions.
Limitation:Represents modeled results and may not reflect observed market outcomes.
Case No. IPC-E-26-08
Attachment 2
Page 1 of 1

BEFORE THE
IDAHO PUBLIC UTILITIES COMMISSION
CASE NO. IPC-E-26-08
IDAHO POWER COMPANY
ATTACHMENT 3

NPSE-Marginal Price Differentials 2026 Marginal Cost-Single Run Method
Summer(June-September) Total Hours %of Total $/MWh 0'r'i'c"'e R at"i'o
Non-Summer(October-May) Total Hours %of Total $/MWh 0'r'i'c"'e R at"i'o
NPSE-Annual Marginal Price 2026 Marginal Cost-Two Run Method
Updated
Case No. |PC-E-26-08
Attachment
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