20250606Supplemental to Application.pdf

INTERMOUNTAIRR) RECEIVED
GAS COMPANY .rune 6, 2025
A Subsidiary of MDU Resources Group,Inc. I DAH O PUBLIC
In the Community to Serve UTILITIES COMMISSION
June 6, 2025
Ms.Monica Barrios-Sanchez
Commission Secretary
Idaho Public Utilities Commission
P.O. Box 83720
Boise, ID 83720-0074
RE: Case No. INT-G-24-05
Dear Ms. Barrios-Sanchez:
Attached for consideration by this Commission is an electronic submission of Intermountain Gas
Company's Supplement to Application for a Determination of 2023 Energy Efficiency Expenses as
Prudently Incurred, including proposed revisions to Rate Schedule EE-RS
If you should have any questions regarding the attached,please don't hesitate to contact me at(208)
377-6015.
Sincerely,
Is/Lori A. Blattner
Lori A. Blattner
Director, Regulatory Affairs
Intermountain Gas Company
Enclosure
cc: Preston Carter

INTERMOUNTAIN GAS COMPANY
CASE NO. INT-G-24-05
SUPPLEMENT
TO
APPLICATION
AND
EXHIBITS
In the Matter of the Application of Intermountain Gas Company for a
Determination of 2023 Energy Efficiency Expenses as Prudently Incurred and
Approval of Rate Schedule EE-RS

Preston N. Carter, ISB No. 8462
Morgan D. Goodin, ISB No. 11184
Givens Pursley LLP
601 W. Bannock St.
Boise, Idaho 83702
Telephone: [phone]
Attorneys for Intermountain Gas Company
BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION
In the Matter of the Application of Case No. INT-G-24-05
INTERMOUNTAIN GAS COMPANY
for a Determination of 2023 Energy SUPPLEMENT TO
Efficiency Expenses as Prudently APPLICATION
Incurred and Approval of Rate Schedule
EE-RS
Intermountain Gas Company("Intermountain"or"Company"),a subsidiary of MDU
Resources Group,Inc.with general offices located at 555 South Cole Road,Boise,Idaho,pursuant
to the Rules of Procedure of the Idaho Public Utilities Commission("Commission"),submits
additional information pertinent to this case in this Supplement ("Supplement to Application" or
"Supplement")to the Application for Determination of 2023 Energy Efficiency Expense as
Prudently Incurred, Case No. INT-G-24-05, filed December 20, 2024 ("Original Application").
This Supplement includes the proposed changes to the Company's Residential Energy
Efficiency Program("EE Program") resulting from applying updated unit energy savings from
the Regional Technical Forum ("RTF") furnace workbook V3.1 released in February 2025. The
information included in this Supplement does not seek to replace, amend, or remove any portion
of the Original Application related to the request for an order designating $3,846,358 of 2023
Energy Efficiency expenditures as prudently incurred. Rather, the Supplement seeks to replace
the proposed Energy Efficiency program revisions provided in the Original Application as
Exhibit No. 2 and the resulting Rate Schedule EE-RS tariff revisions provided in the Original
SUPPLEMENT TO APPLICATION 3

Application as Exhibit No. 3 to reflect the results of incorporating the RTF furnace workbook
changes that became available after this case was filed.
Please address communications regarding this Application to:
Preston N. Carter
Givens Pursley LLP
601 W. Bannock St.
Boise, Idaho 83702
prestoncarter(&aivenspursle.
[e-mail]
[e-mail]
and
Lori A. Blattner
Director—Regulatory Affairs
Intermountain Gas Company
Post Office Box 7608
Boise, ID 83707
[e-mail]
[e-mail]
In support of this Application,Intermountain alleges and states as follows.
INTRODUCTION
Intermountain is a gas utility,subject to the jurisdiction of the Commission,engaged in the
sale of and distribution of natural gas within the State of Idaho under authority of Commission
Certificate No. 219, issued December 2, 1955, as amended and supplemented by Order No. 6564,
dated October 3, 1962.
Intermountain provides natural gas service to the following Idaho communities and counties
and adjoining areas:
Ada County-Boise,Eagle,Garden City,Kuna,Meridian,and Star;
Bannock County-Arimo,Chubbuck,Inkom,Lava Hot Springs,McCammon,and Pocatello;
Bear Lake County- Georgetown and Montpelier;
Bingham County-Aberdeen,Basalt,Blackfoot,Firth,Fort Hall,Moreland/Riverside,and Shelley;
Blaine County-Bellevue,Hailey,Ketchum,and Sun Valley;
Bonneville County-Ammon,Idaho Falls,Iona,and Ucon;
Canyon County-Caldwell,Greenleaf,Middleton,Nampa,Parma,and Wilder;
Caribou County-Bancroft, Grace,and Soda Springs;
SUPPLEMENT TO APPLICATION 4

Cassia County-Burley,Declo,Malta,and Raft River;
Elmore County-Glenns Ferry,Hammett,and Mountain Home;
Fremont County-Parker and St. Anthony;
Gem County-Emmett;
Gooding County-Gooding and Wendell;
Jefferson County-Lewisville,Menan,Rigby,and Ririe;
Jerome County-Jerome;
Lincoln County-Shoshone;
Madison County-Rexburg and Sugar City;
Minidoka County-Heyburn,Paul,and Rupert;
Owyhee County-Bruneau and Homedale;
Payette County-Fruitland,New Plymouth,and Payette;
Power County-American Falls;
Twin Falls County-Buhl,Filer,Hansen,Kimberly,Murtaugh,and Twin Falls;
Washington County-Weiser.
Intermountain's properties in these locations consist of transmission pipelines,liquefied
natural gas storage facilities,compressor stations,distribution mains,services,meters and
regulators, and general plant and equipment.
BACKGROUND
On December 20, 2024, Intermountain filed the Original Application. The Original
Application included proposed revisions to the Company's Residential EE Program based on the
results of the EM&V study and the Company's proposed Technical Reference Manual("IGC
TRM")that incorporated the EM&V results as well as"data sources and analytical methods that are
widely considered acceptable for the measure and purpose"! An important data source for the
Company's proposed IGC TRM is the RTF.
On February 3,2025,the Commission issued a Notice of Application and Notice of
Intervention Deadline in Order No. 36455.
On March 10, 2025, the Commission issued a notice of Modified Procedure in Order No.
36495 setting a comment deadline of June 18,2025 and a reply comment deadline of July 9, 2025.
The Company acknowledges that the filing of this Supplement will likely necessitate a change in the
1 Original Application INT-G-24-05,p 20
SUPPLEMENT TO APPLICATION 5

schedule for this case and will cooperate with the parties to establish a revised schedule.
PROPOSED RESIDENTIAL PROGRAM CHANGES
In February 2025,the RTF released the updated furnace workbook Version 3.1. Since the
RTF is the basis of the underlying savings assumptions in the IGC TRM, Intermountain
commissioned the third parry evaluator("Evaluator')to revise the IGC TRM to update all residential
program incentives with the best available data. After the IGC TRM updates were implemented,
the proposed furnace and smart thermostat measures were not cost effective, and the program
level cost effectiveness resulted in a Utility Cost Test("UCT") of 0.9,which was not cost
effective.
As a result, in this Supplement Intermountain proposes to revise the following program
changes filed in the Original Application, 1)retire the Whole Home Tier II incentive, 2)reduce
the furnace incentive, 3) reduce the tankless water heater incentive and 4)retire the smart
thermostat incentive.
The revised proposed residential energy efficiency program is provided in Exhibit No. 4,
incorporated by reference, which will replace the Original Application Exhibit No. 2. The
Company has also included the updated IGC TRM as Exhibit No. 5 which is incorporated by
reference. Workbook files for these exhibits will be provided with the filing.
PROPOSED TARIFF
The revisions outlined above will also impact the proposed tariff changes in the Original
Application Exhibit No. 4. Exhibit No. 6, incorporated by reference, provides the legislative and
clean copies of the proposed revisions to Rate Schedule EE-RS.
MODIFIED PROCEDURE
Intermountain requests that this matter be handled under modified procedure pursuant to
Rules 201-204 of the Commission's Rules of Procedure. Intermountain stands ready for immediate
SUPPLEMENT TO APPLICATION 6

consideration of this matter.
Because neither the Original Application nor this Supplement propose to change customer
rates, Intermountain has not provided direct notice to customers. See Commission Rule of Procedure
125.01, ADAPA 3.01.01.125.01.
REQUEST FOR RELIEF
Intermountain respectfully petitions the Idaho Public Utilities Commission as follows:
a. That the Commission issue an order designating $3,846,358 of 2023 Energy Efficiency
expenditures as prudently incurred, as requested in the Original Application,
b. That the Commission include this Supplement, the attached Exhibits, and the issues
identified in the Supplement and Exhibits within Case No. INT-G-24-05,
c. That the proposed revisions to Rate Schedule EE-RS shown in Exhibit No. 6 to this
Supplement be accepted as filed,
d. That the Commission approve the requests in the Original Application that are not
altered by this Supplement, including the use of the deemed saving methodology developed and
proposed by the Evaluator and the Company,
e. That the Original Application and Supplement be heard and acted upon without
hearing under modified procedure, and
fh. For such other relief as this Commission may determine just and proper.
DATED: June 6, 2025
9.
INTERMOUNTAIN GAS COMPANY Givens Pursley LLP
By By AlPreston N. Carter
Lori A. Blattner Preston N. Carter
Director—Regulatory Affairs Attorney for Intermountain Gas Company
INTERMOUNTAIN GAS COMPANY Givens Pursley LLP
SUPPLEMENT TO APPLICATION 7

EXHIBIT NO. 4
CASE NO. INT-G-24-05
INTERMOUNTAIN GAS COMPANY
2025 Program Planning
(1 Page)

Exhibit No.4
Case No. INT-G-24-05
Intermountain Gas Company
Page 1 of 1
INTERMOUNTAIN GAS COMPANY
Energy Efficiency Program PROGRAM
2025 Cost-Effectiveness Testing(Program Planning V.2) Rebate Allocation Method %Rebate Count
Residential Overhead Costs $ 810,466.00
INPUT BY REBATE UCT
RESULTS
Amended 2025
ANNUALTHERM INCREMENTAL rebate count
REBATE NAME SEGMENT SAVINGS EUL COST REBATE AMOUNT forecast UCT RATIO
Whole Home I Residential 183 22 $ 3,068 $ 1,500 200 1.1
Whole Home 11 Residential 110 22 $ 2,941 - 0.0
Furnace blended Residential 37 23 $ 228 $ 275 4,900 1.0
Combi boiler Residential 168 25 $ 2,412 $ 1,500 13 1.1
Boiler Residential 107 25 $ 2,135 $ 1,000 13 1.0
Tankless(Energy Star Certified) Residential 51 20 $ 895 $ 375 1 1,500 1.0
Smart Thermostat Residential 26 7 $ 165 0.0
1.0
Indicates a change from Program Proposal V.1.

EXHIBIT NO. 5
CASE NO. INT-G-24-05
INTERMOUNTAIN GAS COMPANY
Updated IGC TRM
(1 page)

Exhibit No.5
Case No.INT-G-24-05
Intermountain Gas Company
Page 1 of 1
Therms per Incremental Measure Life (:02 reduction(to ra Primary Fuel Other Date
Measure Unit cost (Years) over expected Type Sector End-use Technology Other Specifications 1 Specifications 21 Updated Source
measure life)
(1)Must be HERS rated,(2)Air sealing at or below 3 ACH at 50 Pa,(3)Ceiling insulation
at or above R-49,(4)Ducts and air handler located inside conditioned space or duct
leakage to outside of less than 4 CFM25/100 ft'CFA,and(5)Furnace efficiency at or
Whole Home Tier 1 183.40 $3,068.16 22.00 18.66 Gas Residential Space&Water Heating New Construction above 97%AFUE 9/26/2024 PY2021-PY2023 Impact Evaluation
(1)Must be HERS rated,(2)Air sealing at or below 4 ACH at 50 Pa,(3)Ducts and air
handler located inside conditioned space or duct leakage to outside of less than 4
Whole Home Tier 11 110.02 $2,940.86 22.00 17.73 Gas Residential Space&Water Heating New Construction CFM25/100 ft'CFA,and(4)Furnace efficiency at or above 95%AFUE 9/26/2024 PY2021-PY2023 Impact Evaluation
Natural Gas Furnace 95%AFUE
+ 36.18 $250.88 22.50 4.28 Gas Residential Space Heating Gas Furnace Must have AFUE rating equal to or greater than 95% 3/14/2025 Regional Technical Forum Gas Furnace Workbook V3.1
Natural Gas Furnace 97%AFUE
+ 44.10 $20.22 22.50 5.21 Gas Residential Space Heating Gas Furnace Must have AFUE rating equal to or greater than 97% 3/14/2025 Regional Technical Forum Gas Furnace Workbook V3.1
Natural Gas Furnace 95%AFUE
+or 97%AFUE+(Mixed) 36.98 $227.58 22.50 4.37 Gas Residential Space Heating Gas Furnace Must have AFUE rating equal to or greater than 95%or 97% 3/14/2025 Regional Technical Forum Gas Furnace Workbook V3.1
(1)Must be ENERGY STAR qualified;
(2)Must have 7-Day programmable or learning-based scheduling;
(3)Must be Wi-Fi enabled,with remote access;
(4)Must include on-board motion occupancy sensor or be packaged with a motion
sensor. Geo-fencing is not considered motion sensing;
(5)Must have automatic HVAC reduction when home is occupied;
(6)Must minimize auxiliary electric resistance heat runtimes using lockout informed by
outdoor temperature sensor or local weather via internet;
Smart Thermostats 26.29 $165.03 7.00 3.11 Gas Residential Space Heating Smart Thermostat (7)Must be replacing a non-qualifying thermostat 9/26/2024 Regional Technical Forum Connected Thermostats Workbook V3.1
(1)Must be a storage tank gas water heater with less than or equal to 55 gallon tank and
Uniform Energy Factor equal to or greater than 0.64 with medium draw pattern OR
Must be a storage tank gas water heater with less than or equal to 55 gallon tank and
Uniform Energy Factor equal to or greater than 0.68 with high draw pattern OR
Must be a storage tank gas water heater with greater than 55 gallon tank and Uniform
Energy Factor equal to or greater than 0.78 with medium draw pattern OR
Must be a storage tank gas water heater with greater than 55 gallon tank and Uniform
Energy Factor equal to or greater than 0.80 with high draw pattern;
(2)Must be a condensing storage tank water heater;
Storage Tank Water Heater, (3)Must have First Hour Rating of greater than or equal to 51 gallons per hour;
ENERGY STAR-Qualified v4.0 (4)Must have warranty equal to or greater than 6 years system(including parts);
only,condensing 23.14 $1,808.67 14.50 2.29 Gas Residential Water Heating Water Heater (5)Must have safety standards meeting ANSI Z21.10.1/CSA 4.1 9/26/2024 Regional Technical Forum Gas Water Heater Workbook V3.2
(1)Must be a storage tank gas water heater with Uniform Energy Factor equal to or
greater than 0.81 with medium draw pattern OR
Must be a storage tank gas water heater with Uniform Energy Factor equal to or
greater than 0.86 with high draw pattern;
(2)Must be a condensing storage tank water heater;
Storage Tank Water Heater, (3)Must have First Hour Rating of greater than or equal to 67 gallons per hour;
ENERGY STAR-Qualified v5.0, (4)Must have warranty equal to or greater than 6 years system(including parts);
condensing 33.51 $1,808.67 14.50 3.61 Gas Residential Water Heating Water Heater (5)Must have safety standards meeting ANSI Z21.10.1/CSA 4.1 9/26/2024 Regional Technical Forum Gas Water Heater Workbook V3.2
Tankless(Not ENERGY STAR-
qualified) 35.78 $259.53 20.00 4.00 Gas Residential Water Heating Water Heater (1)Must be a tankless gas water heater meeting minimum federal standards 9/26/2024 Regional Technical Forum Gas Water Heater Workbook V3.2
(1)Must be a tankless gas water heater with Uniform Energy Factor equal to or greater
than 0.87;
(2)Must have a GPM of equal to or greater than 2.8 over a 77°rise;
Tankless UEF>_0.87(ENERGY (3)Must have warranty equal to or greater than 6 years on heat exchanger;
STAR V4.0-qualified) 50.25 $727.65 20.00 5.65 Gas Residential Water Heating Water Heater (4)Must have warranty equal to or greater than 5 years on parts 9/26/2024 Regional Technical Forum Gas Water Heater Workbook V3.2
(1)Must be a tankless gas water heater with Uniform Energy Factor equal to or greater
than 0.95;
(2)Must have a GPM of equal to or greater than 2.9 over a 77'rise;
Tankless UEF z 0.95(ENERGY (3)Must have warranty equal to or greater than 6 years on system(incliding parts);
STAR V5.0-qualified) 51.19 $894.79 20.00 5.87 Gas Residential Water Heating Water Heater (4)Must have safety standards meeting ANSI Z21.10.3/CSA 4.3 9/26/2024 Regional Technical Forum Gas Water Heater Workbook V3.2
95%AFUE Boiler 107.12 $2,135.00 25.00 4.28 Gas Residential Space Heating Boiler Must have AFUE rating equal to or greater than 95% 9/26/2024 Illinois Technical Reference Manual V12.0
95%AFUE Combination Boiler 168.25 $2,412.00 25.00 8.27 Gas Residential Space&Water Heating Combination Boilerl Must have AFUE rating equal to or greater than 95% 9/26/2024 Illinois Technical Reference Manual V12.0

EXHIBIT NO. 6
CASE NO. INT-G-24-05
INTERMOUNTAIN GAS COMPANY
Rate Schedule EE-RS
Redline and Clean Tariff
(2 pages)

I.P.U.C. Gas Tariff
Rate Schedules IDAHO PUBLIC UTILITIES COMMISSION
Cn�r+h Fifth Revised Sheet No. 16(Page 2 Approved Effective
of 2
Name May 17, 2022 jug-12022
of Utility Intermountain Gas Company
Rate Schedule EE-RS
RESIDENTIAL ENERGY EFFICIENCY REBATE PROGRAM
(Continued)
REBATES:
Rebate Rebate Type Minimum Efficiency Rating Rebate
Amount
Whole Home Tier I New Tier I Requirements: $9GG1,500
Construction 0 HERS rated
• Air sealing at or below 3 ACH at 50 Pa
• Ceiling insulation at or above R-49
• Ducts and air handler located inside
conditioned space or duct leakage to
outside of less than 4 CFM25/100 ft2 CFA
• Furnace efficiency at or above 97%AFUE
Whele Heme Tier 11 New Tier 11 Requirements: $7-00
GenStFUGtien • HERS rated
• Air sealing at or below 4 ACH at 50 Pa
• D Gts and air handler Iegated inside
eenrli+inned opaGe r d Gt leakage+e
eutskde of loos than it ('FM25/100 f+7 GF
0
Combination Boiler for Space Heating 95%AFUE $N01, 000
Space and Water
Heat
Furnace Space Heating 95%AFUE $a50275
Boiler Space Heating 95%AFUE $N01, 000
Storage Water Heater Water Heating FR�F $44-5
Tankless Water Water Heating .Q1�1 UEFEnergy Star°Certified $35375
Heater Tier I
Tankless Wa+or Water Hooting 87�C $3W
Heater Toe"
Smart Thermostat Them_meostat Energy Star Certified
GENERAL PROVISIONS:
All installations of equipment must comply with all codes and permit requirements applicable in the state
of Idaho and must be properly inspected, if required, by appropriate agencies. Customers must submit
required documentation of purchase and installation to the Company under the Terms and Conditions of
the current rebate program. The Company reserves the right to verify installation prior to the payment of
any rebates.
Issued by: Intermountain Gas Company
By: Lori A. Blattner Title: Director— Regulatory Affairs
€ffeGtiVe: dune 1, 2022

I.P.U.C. Gas Tariff
Rate Schedules
Fifth Revised Sheet No. 16 (Page 2 of 2
Name
of Utility Intermountain Gas Company
Rate Schedule EE-RS
RESIDENTIAL ENERGY EFFICIENCY REBATE PROGRAM
(Continued)
REBATES:
Rebate Rebate Type Minimum Efficiency Rating Rebate
Amount
Whole Home Tier I New Tier I Requirements: $1,500
Construction 0 HERS rated
• Air sealing at or below 3 ACH at 50 Pa
• Ceiling insulation at or above R-49
• Ducts and air handler located inside
conditioned space or duct leakage to
outside of less than 4 CFM25/100 ft2 CFA
• Furnace efficiency at or above 97%AFUE
Combination Boiler for Space Heating 95%AFUE $1,500
Space and Water
Heat
Furnace Space Heating 95%AFUE $275
Boiler Space Heating 95%AFUE $1,000
Tankless Water Water Heating Energy Star'Certified $375
Heater Tier I
GENERAL PROVISIONS:
All installations of equipment must comply with all codes and permit requirements applicable in the state
of Idaho and must be properly inspected, if required, by appropriate agencies. Customers must submit
required documentation of purchase and installation to the Company under the Terms and Conditions of
the current rebate program. The Company reserves the right to verify installation prior to the payment of
any rebates.
Issued by: Intermountain Gas Company
By: Lori A. Blattner Title: Director— Regulatory Affairs