20250305AVU to Staff 1-18.pdf

RECEIVED
AVISTA CORPORATION March 5, 2025
Idaho Public
RESPONSE TO REQUEST FOR INFORMATION Utilities Commission
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-001 TELEPHONE: [phone]
REQUEST:
Please provide the monthly capacity positions for 2025.
RESPONSE:
Here are the monthly capacity positions for 2025 from the 2025 IRP study,these estimates exclude
any planned maintenance.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2025 2025 2025 2025 2025 2025 2025 2025 2025 2025 2025 2025
50 181 330 655 500 197 103 105 440 422 280 153

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-002 TELEPHONE: [phone]
REQUEST:
Table 1 of the Compliance Filing shows that Colstrip Units 3 and 4 will exit in 2025 and Northeast
will exit in 2029. Please explain whether these exits have regulatory certainties such as a signed
contract or a Commission approval. Please also provide the exit dates based on their useful lives.
RESPONSE:
The exit from Colstrip Units 3 & 4 at the end of 2025 is based on a contract signed with
NorthWestern Energy on January 16, 2023, that transfers ownership on January 1, 2026. The exit
from Northeast is an Avista target date. No contract is needed to be signed to exit Northeast since
Avista owns the entire plant and can unilaterally make decisions on the plant. The 2029 exit date
does coincide with the end of the current 5-year air permit test schedule, although the current air
permit expires in 2032.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-003 TELEPHONE: [phone]
REQUEST:
Prior Commission orders such as Order No. 33958 required the Company to use the latest
information for determining capacity deficiency periods. Please respond to the following:
a. Is the load forecast used in the Compliance Filing the latest load forecast?
i.If not,please provide the latest load forecast and explain the difference between the latest
and the proposed load forecast.
b. Is the contract information used for determining capacity deficiency periods the latest contract
information?
i. If not, please provide the latest contract information and explain the difference between
the latest contract information and the proposed contract information.
RESPONSE:
a. Yes. The load forecast used in the Compliance filing is the latest long-term forecast.
b. Yes. The contract information used for determining capacity deficiency includes the latest
contract information.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-004 TELEPHONE: [phone]
REQUEST:
Are Public Utility Regulatory Policies Act ("PURPA") contracts assumed to be renewed in the
Load and Resource Balance? Please explain and justify the decision.
RESPONSE:
Based on Avista's experience with these contracts, as well as ongoing communications with the
project owners, the Company assumes the renewal of these contracts after the term expires. This
has been Avista's policy for the last 20 years at least, regarding PURPA contracts.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-005 TELEPHONE: [phone]
REQUEST:
Please explain why the values in Table 2 of the Compliance Filing do not match the table on the
Tab "Position Summary" of confidential file "AVU-E-25_2025 Capacity Deficiency
Application-Confidential 1-29-25.xlsm". Also,please explain which table is correct.
RESPONSE:
Table 2 was copied and pasted from the position summary tab in the referenced spreadsheet. The 1
MW difference in some of the cells is due to how Word rounds data on tables. They are both
correct,but the spreadsheet would be more accurate given that number of significant digits on each
cell can be expanded.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-006 TELEPHONE: [phone]
REQUEST:
Please define and explain the following resources that are included in Tab "System_LR" of
confidential file "AVU-E-25_2025 Capacity Deficiency Application-Confidential
1-29-25.xlsm" and why their values are zero.
Juris Purch Palouse Wind
Juris Purch Rattlesnake Flat
Juris Purch Kettle Falls
Juris Purch Chelan PUD
Juris Purch Chelan PUD Canadian Entitlement
Juris Purch Columbia Basin Hydro
Juris Purch Clearwater Wind
RESPONSE:
In the event Idaho's jurisdictional allocated share of one of these resources is used to comply with
Washington's CETA on a planning basis, this section of the model would account for the change
in available generation for each state to its position. The amounts moving between jurisdictions is
shown in each individual state's L&R tab. On the system L&R, the movement of generation
balances out to zero since there is no change in the overall utility position by temporarily assigning
generation to an individual jurisdiction.An example of moving generation between jurisdictions is
in Cell DB 172 on the"WA LR"tab".

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-007 TELEPHONE: [phone]
REQUEST:
Please define "Jurisdictional Transfer" and explain why its capacity is zero.
RESPONSE:
Please see the response to Staff PR 006.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-008 TELEPHONE: [phone]
REQUEST:
Please explain how the values of"Short Term Market Purchases"are determined and why they are
not used in calculating Net Position. Also, please explain if the values are subject to a 330 MW
market limitation.
RESPONSE:
The"Short Term Market Purchases" are transactions the utility has committed to at the time of the
IRP. These are typically market transactions for at least one month. These are different than the
330 MW market limitation. The 330 MW market limitation applies to reliability modeling of the
limit we anticipate being able to depend on for market transactions in real time operations during
peak events based on our regional share of the market and transactional history during peak events.
Avista will often buy as much power that is economic considering the ability to deliver the energy
but does not want to depend on market power exceeding 330 MW for resource adequacy.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-009 TELEPHONE: [phone]
REQUEST:
Please define "Embedded EE" and "Selected EE". Please explain the difference between the two
and also explain why their values are the same.
RESPONSE:
Avista's load forecast includes expected energy efficiency savings. Since the IRP must determine
the amount of cost-effective energy efficiency to pursue, the load forecast must estimate the
amount of energy efficiency implied in the load forecast as the model solves for a load without
energy efficiency. To determine how much load to add back to the load forecast, the model is run
iteratively until the amount of energy efficiency selected is similar to the amount added back. The
"Embedded EE"is an estimate of the amount of energy efficiency added to the load forecast from
this iterative process, whereas the "Selected EE" is the actual amount of the model selection.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-010 TELEPHONE: [phone]
REQUEST:
Please explain what"Electrification"represents and why its values are zero.
RESPONSE:
The "Electrification" cells are all zero in the expected or base case. These cells are only used in
2025 IRP scenarios studying additional electrification of building stock where electricity replaces
natural gas use not already embedded in the load forecast.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: John Lyons
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-0I I TELEPHONE: [phone]
REQUEST:
For the line item"Reserves + Regulation+ Maintenance Adjustment", please define "Reserves",
"Regulation" and"Maintenance Adjustment" and explain how their values are determined. Also,
please explain the difference between"Reserves" and"Regulation."
RESPONSE:
These are a total of adjustments used in the IRP where the amounts individually may provide
information to the general public that is confidential. Since Avista makes its PRiSM model public,
these values are summed.
"Reserves" is the account of the operating reserves Avista must hold for loads and generators
within its balancing authority. For loads, this is 3% of load. Avista also carries reserves for two
generators not serving Avista customers.
"Regulation" accounts for the difference between the average load of the peak hour versus the
absolute peak load within the hour. Avista assumes this is 10 MW.
The "Maintenance Adjustment" is an adjustment to the peak planning forecast to account for unit
maintenance using a combination of historical outages and a forecast of routine maintenance.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-012 TELEPHONE: [phone]
REQUEST:
Please explain why the Planning Reserve Margin("PRM")for winter is determined by a reliability
study, while the PRM for summer is determined by the single largest contingency resource
compared to expected load. Also, please explain the rationale behind the method for summer
PRM. Lastly, please explain if the reliability study that determines PRM uses the Qualifying
Capacity Contribution ("QCCs") in 2030 derived from the short-term Western Resource
Adequacy Program ("WRAP") QCCs.
RESPONSE:
When Avista conducted its hourly reliability planning study, the study found the primary capacity
shortfalls are in the winter months. When determining the planning reserve margin (PRM), the
resources added to meet winter capacity shortfalls also would meet the smaller summer
requirements. Since IRP planning requires a PRM in all months in the event a resource is added to
solve a particular season, Avista needed a summer PRM as the utility could be short in this season
if winter only resources are added. Avista decided to use the single largest contingency method to
arrive at this estimate. This method quantifies the amount of lost generation of the single largest
facility in the event it went on outage. In this case, Coyote Springs 2 is assumed to generate 288
MW in a summer peak event and peak summer load is approximately 1,837 MW,dividing the two
results is a 16% factor. Since Avista is at risk of losing this asset, the 16% summer PRM seemed
reasonable to ensure the utility has adequate capacity in this season. Absent this PRM, the utility
could be overly dependent on the market.
Regarding QCCs, Avista's reliability study does not use the WRAP's QCC values, the study is
based on the capability of each resource using 1,000 simulations of load, forced outages, wind,
temperatures, and hydro conditions. The WRAP QCC values are only used as the capacity value
for estimating the PRM based upon the resource capacity shortfall from the resource adequacy
study.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/0/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-013 TELEPHONE: [phone]
REQUEST:
Page 6 states that Avista conducts a reliability study with the resources chosen within the Preferred
Resource Strategy for 2030, and the results show the system is below the 5% Loss of Load
Probability("LOLP")threshold. Please explain if it is possible for the LOLP to be above 5%if the
PRM is selected using the 5%LOLP threshold and resources are selected based on the PRM. If so,
please explain how that would occur.
RESPONSE:
If the PRS resulted in a portfolio with a LOLP above 5%,the PRM would be increased, and a new
portfolio would be created to ensure the resulting portfolio's PRM is below 5%. This did occur in
high load scenarios where additional capacity added did not meet the 5%threshold with the higher
loads.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-014 TELEPHONE: [phone]
REQUEST:
Page 5 of the Compliance Filing states that using the WRAP values creates a consistency of
resource assumptions in other resource adequacy settings. Please explain what are "other resource
adequacy settings" and why the consistency of resource assumptions is important.
RESPONSE:
The "other resource adequacy setting" is compliance with the WRAP and for Avista's internal
L&R tracking. Avista is a participant in the WRAP and finds this is the best method to account for
L&R balancing as it creates a consistent methodology between all participating utilities of how to
estimate the capacity value of each resource. If Avista did not use a consistent method of capacity
quantification it would have multiple estimates of how much capacity an individual resource is
assumed to meet peak load events. This would result in duplication of analysis and tracking.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-015 TELEPHONE: [phone]
REQUEST:
Please provide examples showing how WRAP short-term QCCs are converted to long-term QCCs.
RESPONSE:
See the confidential attachment Staff_PR_015_Attachment A. This attachment is currently being
prepared for use in Avista's upcoming Request for Proposals for new capacity. This file includes
the WRAP's estimated ELCC value for VERB and energy storage(WRAP QCC Linear tab). These
estimates are for the amount of effective load carrying (ELCC) for the year for each resource for
the current generation level in the region and for if the region adds generation. These ELCC
changes are then applied to the QCCs the WRAP currently estimates for each month (See
"Monthly QCC" tab). Avista forecasts the change based upon its regional forecast for growth of
each resource type in tab "QCC WRAP Forecast". The remaining tab "E3 study reference" is a
comparison as it is an independent view of how ELCC/QCC values will change over time. Avista
is currently working with E3 to conduct an updated study on regional resource adequacy along
with other utilities in the Northwest.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-016 TELEPHONE: [phone]
REQUEST:
Page 6 of the Compliance Filing states that if Avista used the prior methodology approved in past
orders for resource capacity contribution, the resulting capacity need would be the same. Please
provide the following:
a. Please explain how the prior methodology determined resource capacity contribution and
provide examples for each technology type.
b. Please explain how WRAP method determines short-term QCCs and provide examples for each
technology type.
c. Please explain how Avista determined long-term QCCs and provide examples for each
technology type.
RESPONSE:
a. The prior methodology could have assigned a higher or lower capacity value for each
resource. This could be because Avista did not include forced outages in its methodology
to account for generation capacity or if the variable resource had a different resulting
effective load carrying capability assumed depending on the methodology of the study of
the resource. For example, Coyote Springs 2 has a 314 MW QCC value by the WRAP, if
Avista used its prior methodology it would be 317.5 MW. The WRAP determines its value
by historical forced outage rates and specific historical generation resource submittals.
b. Please see Confidential Staff_PR_016 Attachment A pages 17 to 34 for detailed
documentation about the WRAP methodology for the calculation of short-term QCCs for
all resource types including thermal or long duration storage resources (p. 17 — 21),
variable energy resources (p. 22—29), energy storage(p. 29—30),hybrid facilities (p. 30 -
31), and hydro resources (p. 31 —34).
c. See Response to Staff_PR 015 for an example. The WRAP's study results for bother
winter and summer periods if additional resource capacity is added to the system are shown
in Confidential Staff_PR_016 Attachment B (2024-12-12 Webinar Summer 2026 and
2029 Data final.pdf) and Confidential Staff_PR_016 Attachment C (2024-06-13 Webinar
Winter 2025-2026 and 2028-2029 Data.pdf).

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-017 TELEPHONE: [phone]
REQUEST:
Page 6 of the Compliance Filing states that Avista uses the resource adequacy study to calculate its
resource deficit.Please explain the method used in the resource adequacy study and provide a copy
of the study. Also, please explain the relationship between the deficit amount determined in the
resource adequacy study and the deficit amount determined by the Load and Resource Balance.
RESPONSE:
The confidential resource adequacy study documents are included as:
• Staff_PR_017 Attachment A
• Staff PR 017 Attachment B
Attachment A contains a summary of the 1,000 simulations, including the quantity and size of
resource deficits, this file also demonstrates how the 24% Planning Reserve Margin (PRM) is
calculated in the L&R 2030 tab, in this case 50 MW is added to the January month to arrive at the
24%PRM value,whereas the 50 MW addition was required to get close to the 5%LOLP target in
2030.Attachment B is the model used to estimate our capacity shortfalls. The results of this model
are input into Attachment A. The model runs each simulation one at a time then stores the results.
In this example,the 1,000 simulations were split between 5 files and only the first 200 simulations
are included as an example.
There is one major difference regarding the differences between this result and the L&R. The
difference is the L&R used in the IRP includes the maintenance outages discussed in the response
to Staff PR_011.

AVISTA CORPORATION
RESPONSE TO REQUEST FOR INFORMATION
JURISDICTION: IDAHO DATE PREPARED: 03/05/2025
CASE NO: AVU-E-25-02 WITNESS: James Gall
REQUESTER: IPUC RESPONDER: James Gall
TYPE: Production Request DEPARTMENT: Resource Planning
REQUEST NO.: Staff-018 TELEPHONE: [phone]
REQUEST:
Page 5 of the Compliance Filing states that the PRM is determined by summing the QCCs of all
existing and "required" resources to determine the 5% LOLP result and then dividing it by the
expected peak load. In reference to Table 3 of the Compliance Filing,does the"required"resource
mean the 50-MW resource? Please explain whether the 50-MW resource is determined based on
the 5% LOLP target under both Method 1 and/or Method 2.
RESPONSE:
The reference is referring to the requirement of needing a 50 MW resource. The 50 MW resource
is needed in both Method 1 and Method 2 as the resource need is being identified in the resource
adequacy model, not the L&R. The L&R is used for the Planning Reserve Margin calculation.