20250530Park Exhibit Nos. 27-28.pdf

Preston N. Carter, ISB No. 8462
Megann E. Meier, ISB No. 11948
GIVENS PURSLEY LLP
601 West Bannock Street
P.O. Box 2720
Boise, Idaho 83701-2720
Office: [phone]
Fax: [phone]
[e-mail]
[e-mail]
Attorneys for Intermountain Gas Company
BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION
IN THE MATTER OF THE APPLICATION Case No. INT-G-25-02
OF INTERMOUNTAIN GAS COMPANY
FOR THE AUTHORITY TO INCREASE
ITS RATES AND CHARGES FOR
NATURAL GAS SERVICE IN THE STATE
OF IDAHO
EXHIBIT 27 TO ACCOMPANY THE
DIRECT TESTIMONY OF MIN PARK

RS_2025_LOGP_NOAUG_WITHOUT_AR
AR REMOVED, NO AUG HDD
Dependent Variable:THERMS
Method: Least Squares
Sample:2007M0l 2024M12
Included observations:216
Variable Coefficient Std. Error t-Statistic Prob.
C 20.23785 3.59600 5.62788 0.00000
Jan-65 0.11258 0.00098 114.89185 0.00000
Feb-65 0.11255 0.00116 96.79047 0.00000
Mar-65 0.10903 0.00135 80.92375 0.00000
Apr-65 0.09950 0.00189 52.54880 0.00000
May-65 0.08842 0.00287 30.81813 0.00000
Jun-65 0.08804 0.00596 14.77116 0.00000
Jul-65 0.05950 0.01750 3.40061 0.00081
Sep-65 0.04780 0.01898 2.51848 0.01256
Oct-65 0.08219 0.00507 16.20111 0.00000
Nov-65 0.09406 0.00214 43.94098 0.00000
Dec-65 0.10763 0.00122 87.88453 0.00000
SUMMER 4.40118 1.10469 3.98409 0.00009
LOGP -2.46605 0.82386 -2.99328 0.00310
R-squared 0.9970 Mean dependent var 61.98756793
Adjusted R-squared 0.9968 S.D.dependent var 44.83515336
S.E. of regression 2.5462 Akaike info criterion 4.769691033
Sum squared resid 1309.5813 Schwarz criterion 4.988459078
Log likelihood -501.1266 Hannan-Quinn criter. 4.858073859
F-statistic 5112.5007 Durbin-Watson stat 0.807544253
Prob(F-statistic) 0.0000
Case No.INT-G-25-02
M.Park,IGC
Exhibit No. 27
Pagel of 8

RS_2025_L O G P_A U G_W I T H O U T_A R
AR REMOVED,AUG HDD
Dependent Variable:THERMS
Method: Least Squares
Sample:2007M0l 2024M12
Included observations:216
Variable Coefficient Std. Error t-Statistic Prob.
C 20.41901 3.61788 5.64392 0.00000
Jan-65 0.11258 0.00098 114.69151 0.00000
Feb-65 0.11255 0.00116 96.62213 0.00000
Mar-65 0.10904 0.00135 80.78307 0.00000
Apr-65 0.09951 0.00190 52.45885 0.00000
May-65 0.08843 0.00287 30.76654 0.00000
Jun-65 0.08805 0.00597 14.74708 0.00000
Jul-65 0.06296 0.01866 3.37421 0.00089
Aug-65 0.06046 0.11186 0.54048 0.58946
Sep-65 0.05142 0.02016 2.55100 0.01149
Oct-65 0.08220 0.00508 16.17448 0.00000
Nov-65 0.09406 0.00214 43.86540 0.00000
Dec-65 0.10763 0.00123 87.73093 0.00000
SUMMER 4.24079 1.14573 3.70139 0.00028
LOGP -2.50920 0.82916 -3.02619 0.00280
R-squared 0.9970 Mean dependent var 61.98756793
Adjusted R-squared 0.9968 S.D.dependent var 44.83515336
S.E.of regression 2.5507 Akaike info criterion 4.77749802
Sum squared resid 1307.6808 Schwarz criterion 5.011892354
Log likelihood -500.9698 Hannan-Quinn criter. 4.872193905
F-statistic 4730.7066 Durbin-Watson stat 0.805345395
Prob(F-statistic) 0.0000
Case No.INT-G-25-02
M.Park,IGC
Exhibit No. 27
Page 2 of 8

RS Proposed Model
RS_2025_LOGP
PRICE-NATURAL LOG
Dependent Variable:THERMS
Method:ARMA Conditional Least Squares(Marquardt-EViews legacy)
Sample(adjusted):2007M022024M12
Included observations:215 after adjustments
Convergence achieved after 8 iterations
Variable Coefficient Std. Error t-Statistic Prob.
C 21.474957 6.800770 3.157725 0.001836
Jan-65 0.111551 0.000797 139.887181 0.000000
Feb-65 0.111410 0.000949 117.358381 0.000000
Mar-65 0.107525 0.001098 97.885782 0.000000
Apr-65 0.097481 0.001528 63.789024 0.000000
May-65 0.084760 0.002267 37.388586 0.000000
Jun-65 0.081023 0.004736 17.106224 0.000000
Jul-65 0.057419 0.011640 4.932893 0.000002
Sep-65 0.048931 0.012387 3.950241 0.000108
Oct-65 0.075692 0.003942 19.200212 0.000000
Nov-65 0.091554 0.001654 55.339293 0.000000
Dec-65 0.106381 0.000975 109.061575 0.000000
SUMMER 2.729326 0.865976 3.151734 0.001872
LOG(PRICE) -2.447996 1.592126 -1.537564 0.125736
AR(1) 0.610449 0.055868 10.926553 0.000000
R-squared 0.9981 Mean dependent var 61.6223
Adjusted R-square 0.9979 S.D.dependent var 44.6165
S.E.of regression 2.0211 Akaike info criterion 4.3124
Sum squared resid 817.0082 Schwarz criterion 4.5476
Log likelihood -448.5855 Hannan-Quinn criter. 4.4074
F-statistic 7434.4146 Durbin-Watson stat 2.1038
Prob(F-statistic) 0.0000
Inverted AR Roots 0.61
Case No.INT-G-25-02
M.Park,IGC
Exhibit No. 27
Page 3 of 8

RS Staff Proposed Model
RS 2025 YEAR YEARA2 NOAUG WITHOUT AR LOGP
AR and LOGP REMOVED, NO AUG HDD
Dependent Variable:THERMS
Method: Least Squares
Sample(adjusted):2007M0l2024M12
Included observations:216 after adjustments
Variable Coefficient Std. Error t-Statistic Prob.
C 118550.7 24887.24 4.76351 0.00000
Jan-65 0.11313 0.00084 135.51610 0.00000
Feb-65 0.11317 0.00099 114.18540 0.00000
Mar-65 0.10962 0.00115 95.60540 0.00000
Apr-65 0.10024 0.00161 62.20175 0.00000
May-65 0.08963 0.00244 36.70035 0.00000
Jun-65 0.09124 0.00508 17.97104 0.00000
Jul-65 0.06290 0.01479 4.25377 0.00000
Sep-65 0.05826 0.01612 3.61484 0.00040
Oct-65 0.08585 0.00434 19.80482 0.00000
Nov-65 0.09545 0.00183 52.24237 0.00000
Dec-65 0.10839 0.00104 103.79060 0.00000
SUMMER 4.76691 0.93817 5.08109 0.00000
YEAR -117.87210 24.69564 -4.77299 0.00000
YEAR A2 0.029301 0.006126 4.782827 0.0000
R-squared 0.99785 Mean dependent var 61.98757
Adjusted R-squared 0.99770 S.D.dependent var 44.83515
S.E. of regression 2.15257 Akaike info criterion 4.438121
Sum squared resid 931.3488 Schwarz criterion 4.672516
Log likelihood -464.3171 Hannan-Quinn criter. 4.532817
F-statistic 6648.0540 Durbin-Watson stat 1.156195
Prob(F-statistic) 0.0000
Case No.INT-G-25-02
M.Park,IGC
Exhibit No. 27
Page 4 of 8

GS_2025_LOGP_NOAUG_NOJULY_WITHOUT_AR
AR REMOVED,AUG AND JUL REMOVED
Dependent Variable:THERMS
Method: Least Squares
Sample:2007M0l 2024M12
Included observations:216
Variable Coefficient Std. Error t-Statistic Prob.
C 263.11539 33.35710 7.88784 0.00000
Jan-65 0.50174 0.00936 53.59885 0.00000
Feb-65 0.50186 0.01109 45.25574 0.00000
Mar-65 0.48680 0.01274 38.20752 0.00000
Apr-65 0.42869 0.01793 23.91030 0.00000
May-65 0.36918 0.02714 13.60468 0.00000
Jun-65 0.36359 0.05495 6.61619 0.00000
Sep-65 0.28877 0.14405 2.00456 0.04634
Oct-65 0.39244 0.04539 8.64646 0.00000
Nov-65 0.38028 0.01994 19.07049 0.00000
Dec-65 0.46899 0.01167 40.20206 0.00000
SUMMER 31.72998 10.41253 3.04729 0.00262
LOGP -46.22769 7.58811 -6.09213 0.00000
R-squared 0.9866 Mean dependent var 304.0415
Adjusted R-squared 0.9858 S.D.dependent var 203.018
S.E.of regression 24.2013 Akaike info criterion 9.268988
Sum squared resid 118897.7379 Schwarz criterion 9.47213
Log likelihood -988.0507 Hannan-Quinn criter. 9.351058
F-statistic 1243.8908 Durbin-Watson stat 0.577192
Prob(F-statistic) 0.0000
El
Case No.INT-G-25-02
M.Park,IGC
Exhibit No. 27
Page 5 of 8

GS_2025_LOG P_AUG_WITHO UT_AR
AR REMOVED,AUG HDD
Dependent Variable:THERMS
Method: Least Squares
Sample:2007M0l 2024M12
Included observations:216
Variable Coefficient Std. Error t-Statistic Prob.
C 264.24500 33.59509 7.86558 0.00000
Jan-65 0.50174 0.00939 53.43377 0.00000
Feb-65 0.50187 0.01112 45.11673 0.00000
Mar-65 0.48680 0.01278 38.08999 0.00000
Apr-65 0.42872 0.01798 23.83804 0.00000
May-65 0.36924 0.02722 13.56448 0.00000
Jun-65 0.36367 0.05512 6.59723 0.00000
Jul-65 0.13824 0.16834 0.82120 0.41251
Aug-65 0.48825 0.88935 0.54900 0.58361
Sep-65 0.35677 0.16482 2.16460 0.03160
Oct-65 0.39251 0.04553 8.62113 0.00000
Nov-65 0.38030 0.02000 19.01262 0.00000
Dec-65 0.46899 0.01170 40.07777 0.00000
SUMMER 28.12421 11.25488 2.49885 0.01326
LOGP -46.49623 7.64506 -6.08187 0.00000
R-squared 0.9866 Mean dependent var 304.0414569
Adjusted R-squared 0.9857 S.D.dependentvar 203.0180054
S.E.of regression 24.2763 Akaike info criterion 9.283792362
Sum squared resid 118456.9419 Schwarz criterion 9.518186696
Log likelihood -987.6496 Hannan-Quinn criter. 9.378488247
F-statistic 1059.6696 Durbin-Watson stat 0.565049225
Prob(F-statistic) 0.0000
Case No.INT-G-25-02
M.Park,IGC
Exhibit No. 27
Page 6 of 8

GS Proposed Model
GS_2025_LOGP
PRICE-NATURAL LOG
Dependent Variable:THERMS
Method:ARMA Conditional Least Squares(Marquardt-EViews legacy)
Sample(adjusted):2007M022024M12
Included observations:215 after adjustments
Convergence achieved after 8 iterations
Variable Coefficient Std. Error t-Statistic Prob.
C 248.1781 72.2096 3.4369 0.0007
Jan-65 0.4999 0.0066 75.7699 0.0000
Feb-65 0.5002 0.0079 63.7107 0.0000
Mar-65 0.4816 0.0090 53.4960 0.0000
Apr-65 0.4206 0.0125 33.7739 0.0000
May-65 0.3512 0.0183 19.1740 0.0000
Jun-65 0.3252 0.0366 8.8751 0.0000
Sep-65 0.2950 0.0841 3.5093 0.0006
Oct-65 0.3560 0.0299 11.9213 0.0000
Nov-65 0.3679 0.0131 28.0070 0.0000
Dec-65 0.4643 0.0080 57.9092 0.0000
SUMMER 20.9171 7.0741 2.9569 0.0035
LOG(PRICE) -41.1575 16.8900 -2.4368 0.0157
AR(1) 0.7250 0.0495 14.6359 0.0000
R-squared 0.9934 Mean dependent var 302.4075
Adjusted R-square 0.9930 S.D.dependent var 202.0631
S.E. of regression 16.9372 Akaike info criterion 8.5598
Sum squared resic 57660.4036 Schwarz criterion 8.7793
Log likelihood -906.1782 Hannan-Quinn criter. 8.6485
F-statistic 2327.4881 Durbin-Watson stat 2.1089
Prob(F-statistic) 0.0000
Inverted AR Roots 0.72
Case No.INT-G-25-02
M.Park,IGC
Exhibit No. 27
Page 7 of 8

GS Staff Proposed Model
GS 2025 YEAR YEARA2 NOAUG NOJULY WITHOUT AR LOGP
AR and LOGP REMOVED,JUL and AUG HDD REMOVED
Dependent Variable:THERMS
Method: Least Squares
Sample(adjusted):2007M0l2024M12
Included observations:216 after adjustments
Variable Coefficient Std. Error t-Statistic Prob.
C 844317.5 209672.30 4.02684 0.00010
Jan-65 0.51112 0.00707 72.30709 0.00000
Feb-65 0.51255 0.00838 61.16803 0.00000
Mar-65 0.49738 0.00961 51.75251 0.00000
Apr-65 0.44082 0.01353 32.59287 0.00000
May-65 0.38773 0.02047 18.94541 0.00000
Jun-65 0.40915 0.04147 9.86718 0.00000
Sep-65 0.38946 0.10825 3.59764 0.00040
Oct-65 0.44208 0.03435 12.87110 0.00000
Nov-65 0.40079 0.01508 26.58294 0.00000
Dec-65 0.48212 0.00882 54.69457 0.00000
SUMMER 38.09587 7.84324 4.85716 0.00000
YEAR -841.26550 208.05760 -4.04343 0.00010
YEAR A2 0.20957 0.05161 4.06026 0.00010
R-squared 0.99251 Mean dependent var 304.0415
Adjusted R-squared 0.99203 S.D.dependentvar 203.018
S.E. of regression 18.12236 Akaike info criterion 8.69479
Sum squared resid 66340.8600 Schwarz criterion 8.913558
Log likelihood -925.0373 Hannan-Quinn criter. 8.783172
F-statistic 2060.0180 Durbin-Watson stat 1.062253
Prob(F-statistic) 0.0000
Case No.INT-G-25-02
M.Park,IGC
Exhibit No. 27
Page 8 of 8

Preston N. Carter, ISB No. 8462
Megann E. Meier, ISB No. 11948
GIVENS PURSLEY LLP
601 West Bannock Street
P.O. Box 2720
Boise, Idaho 83701-2720
Office: [phone]
Fax: [phone]
[e-mail]
[e-mail]
Attorneys for Intermountain Gas Company
BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION
IN THE MATTER OF THE APPLICATION Case No. INT-G-25-02
OF INTERMOUNTAIN GAS COMPANY
FOR THE AUTHORITY TO INCREASE
ITS RATES AND CHARGES FOR
NATURAL GAS SERVICE IN THE STATE
OF IDAHO
EXHIBIT 28 TO ACCOMPANY THE
DIRECT TESTIMONY OF MIN PARK

Intermountain Gas Company
Weather Normalization Adjustment
For the Test Year Ending December 31,2024
Line
No. Description Jan-24 Feb-24 Mar-24 Apr-24 May-24 Jun-24 Jul-24 Aug-24 Sep-24 Oct-24 Nov-24 Dec-24 Total
1 IRS
2 HDD65:
3 Actual Degree Days 1,137.10 862.21 776.31 619.33 423.44 192.35 34.85 1.75 21.50 106.36 439.51 881.03 5,495.74
4 Normal Degree Days 1,201.52 964.82 853.92 642.42 433.19 195.75 54.06 3.65 26.29 205.23 484.53 885.59 5,950.96
5 Difference -warmer-colder 64.411110 102.607010 77.607810 23.097120 9.751330 3.396970 19.211480 1.898880 4.789780 98.87 45.02 4.56 455.23
6 Model Coefficient x Difference 0.113127 0.113167 0.109620 0.100243 0.089630 0.091235 0.062904 0.000000 0.058264 0.085852 0.095446 0.108387
7 Change in Therms/Customer 7.28664 11.61173 8.50737 2.31532 0.87401 0.30992 1.20848 0.00000 0.27907 8.49 4.30 0.49 45.67
8 Customers 383,059 383,766 384,508 385,223 385,575 385,872 386,302 386,811 387,364 388,842 389,665 392,064 4,639,051
9 HDD65 Therm Adjustment 2,791,213 4,456,187 3,271,152 891,915 336,996 119,589 466,838 0 108,102 3,300,588 1,674,480 193,829 17,610,889
10 GS-1:
11 HDD65:
12 Actual Degree Days 1,173.60 868.83 801.55 637.86 437.32 202.70 37.62 2.17 25.70 114.17 472.05 899.24 5,672.80
13 Normal Degree Days 1,232.63 988.73 877.50 661.29 446.33 205.83 57.65 4.93 33.22 223.95 511.86 909.19 6,153.09
14 Difference +warmer-colder 59.030370 119.903230 75.946080 23.424630 9.006020 3.123210 20.031430 2.755560 7.520730 109.78 39.82 9.95 480.29
15 Model Coefficient x Difference 0.511122 0.512548 0.497380 0.440823 0.387725 0.409150 0.000000 0.000000 0.389455 0.442078 0.400787 0.482117
16 Change in Therms/Customer 30.17172 61.45616 37.77406 10.32612 3.49186 1.27786 0.00000 0.00000 2.92899 48.53215 15.95889 4.79496 216.71
17 Customers(with Migration Adjustment) 36,102 36,167 36,220 36,219 36,222 36,180 36,148 36,142 36,134 36,198 36,263 36,605 434,600
18 HDD65 Therm Adjustment 1,089,259 2,222,685 1,368,176 374,002 126,482 46,233 0 0 105,836 1,756,767 578,717 175,520 7,843,677
19 Total Therm Adjustment 3,880,472 6,678,872 4,639,328 1,265,917 463,478 165,822 466,838 - 213,938 5,057,355 2,253,197 369,349 25,454,566
Case No.INT-G-25-02
M.Park,IGC
Exhibit No.28
Page 1 of 1