# Appendix A: Utility Bill Analysis to Determine Electrical Energy Savings

Table A.1 presents the monthly electricity use in Fort Polk's North and
South Fort areas for the last 12 months of the pre-retrofit period and
the first 12 months of the post-retrofit period. Also included are the
monthly base-65°F heating and cooling degree days (HDD and CDD).

> Table A.1. Pre- and post-retrofit monthly electricity use and
> base-65°F heating and cooling degree days for North Fort and South
> Fort, Fort Polk

+---+-----------+--------+--------+------------------+---------------+
|   |           |        |        | Monthly          |               |
|   |           |        |        | electricity use  |               |
|   |           |        |        | (kWh)            |               |
+---+-----------+--------+--------+------------------+---------------+
|   | Month     | HDD    | CDD    | South Fort       | North Fort    |
+---+-----------+--------+--------+------------------+---------------+
| > | Mar-94    | 182    | 50     | 10,791,312       | 2,334,600     |
|   |           |        |        |                  |               |
| P |           |        |        |                  |               |
| r |           |        |        |                  |               |
| e |           |        |        |                  |               |
| - |           |        |        |                  |               |
| r |           |        |        |                  |               |
| e |           |        |        |                  |               |
| t |           |        |        |                  |               |
| r |           |        |        |                  |               |
| o |           |        |        |                  |               |
| f |           |        |        |                  |               |
| i |           |        |        |                  |               |
| t |           |        |        |                  |               |
+---+-----------+--------+--------+------------------+---------------+
|   | Apr-94    | 66     | 155    | 11,711,616       | 2,323,650     |
+---+-----------+--------+--------+------------------+---------------+
|   | May-94    | 7      | 231    | 13,867,308       | 2,686,450     |
+---+-----------+--------+--------+------------------+---------------+
|   | Jun-94    | 0      | 450    | 16,129,008       | 3,325,700     |
+---+-----------+--------+--------+------------------+---------------+
|   | Jul-94    | 0      | 486    | 17,445,540       | 3,511,700     |
+---+-----------+--------+--------+------------------+---------------+
|   | Aug-94    | 0      | 451    | 17,338,440       | 3,518,200     |
+---+-----------+--------+--------+------------------+---------------+
|   | Sep-94    | 4      | 323    | 15,002,316       | 2,908,100     |
+---+-----------+--------+--------+------------------+---------------+
|   | Oct-94    | 57     | 165    | 12,693,408       | 2,454,750     |
+---+-----------+--------+--------+------------------+---------------+
|   | Nov-94    | 118    | 60     | 10,116,372       | 2,114,200     |
+---+-----------+--------+--------+------------------+---------------+
|   | Dec-94    | 346    | 13     | 10,521,756       | 2,241,150     |
+---+-----------+--------+--------+------------------+---------------+
|   | Jan-95    | 424    | 12     | 11,405,604       | 2,629,900     |
+---+-----------+--------+--------+------------------+---------------+
|   | Feb-95    | 276    | 7      | 9,874,032        | 2,252,550     |
+---+-----------+--------+--------+------------------+---------------+
| > | Sep-96    | 5      | 331    | 13,112,400       | 2,720,950     |
|   |           |        |        |                  |               |
| P |           |        |        |                  |               |
| o |           |        |        |                  |               |
| s |           |        |        |                  |               |
| t |           |        |        |                  |               |
| - |           |        |        |                  |               |
| r |           |        |        |                  |               |
| e |           |        |        |                  |               |
| t |           |        |        |                  |               |
| r |           |        |        |                  |               |
| o |           |        |        |                  |               |
| f |           |        |        |                  |               |
| i |           |        |        |                  |               |
| t |           |        |        |                  |               |
+---+-----------+--------+--------+------------------+---------------+
|   | Oct-96    | 41     | 147    | 10,815,084       | 2,240,500     |
+---+-----------+--------+--------+------------------+---------------+
|   | Nov-96    | 190    | 45     | 9,057,972        | 1,984,100     |
+---+-----------+--------+--------+------------------+---------------+
|   | Dec-96    | 311    | 21     | 9,313,584        | 2,013,200     |
+---+-----------+--------+--------+------------------+---------------+
|   | Jan-97    | 486    | 35     | 10,412,220       | 2,571,250     |
+---+-----------+--------+--------+------------------+---------------+
|   | Feb-97    | 321    | 23     | 8,923,068        | 2,146,850     |
+---+-----------+--------+--------+------------------+---------------+
|   | Mar-97    | 80     | 86     | 9,522,492        | 2,128,550     |
+---+-----------+--------+--------+------------------+---------------+
|   | Apr-97    | 86     | 48     | 9,299,304        | 2,011,800     |
+---+-----------+--------+--------+------------------+---------------+
|   | May-97    | 0      | 251    | 11,893,980       | 2,334,900     |
+---+-----------+--------+--------+------------------+---------------+
|   | Jun-97    | 0      | 401    | 13,884,024       | 3,033,450     |
+---+-----------+--------+--------+------------------+---------------+
|   | Jul-97    | 0      | 564    | 15,681,624       | 3,455,950     |
+---+-----------+--------+--------+------------------+---------------+
|   | Aug-97    | 0      | 511    | 15,210,300       | 3,389,450     |
+---+-----------+--------+--------+------------------+---------------+

To normalize electricity use to a typical year at the site, we fit the
pre- and post-retrofit monthly electrical energy use for each area of
the base to a function of heating and cooling degrees:

E (kWh) = a + h · HDD + c · CDD

Then, since a typical year at Fort Polk contains 1909 heating degree
days and 2493 cooling degree days, the energy use in a typical year is
12 · a + 1909 · h + 2493 · c.

The regression equations are as follows:

> [Pre-retrofit]{.underline}
>
> North Fort: E = 1,712,029 + 1,829 · HDD + 3,766 · CDD
>
> South Fort: E = 9,177,092 + 3,638 · HDD + 17,223 · CDD
>
> [Post-retrofit]{.underline}
>
> North Fort: E = 1,636,307 + 1,457 · HDD + 3,322 · CDD
>
> South Fort: E = 8,376,563 + 2,249 · HDD + 13,475 · CDD

Substituting in the heating and cooling degree days for a typical year
into each of the four equations in turn gives the results shown in Table
A.2, which also provides estimated 95% confidence intervals for each of
the parameters, obtained using a bootstrap technique (Davison 1997).

Table A.2. Weather-normalized annual electricity use (million kWh)

  ---------------- ----------------- ------------------- -----------------
                   Pre-retrofit      Post-retrofit       Savings

  North Fort       33.4 ± 0.6        30.8 ± 0.6          2.7 ± 0.9

  South Fort       160.0 ± 3.4       138.4 ± 2.0         21.6 ± 3.9

  Total            193.4 ± 3.4       169.2 ± 2.1         24.3 ± 4.0
  ---------------- ----------------- ------------------- -----------------

Statistical analyses of the regression equations are presented in tables
A.3 through A.6.

Table A.3. Regression analysis of pre-retrofit monthly energy use in
North Fort

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      1,712,029      92,196         18.6           1.75E--08

  HDD            1,829          324            5.7            3.12E--04

  CDD            3,766          263            14.3           1.67E--07

  R-squared:                    0.9713                        

  Adjusted                      0.965                         
  r-squared:                                                  
  -------------- -------------- -------------- -------------- --------------

Table A.4. Regression analysis of pre-retrofit monthly energy use in
South Fort

  -------------- -------------- -------------- -------------- --------------
                 Coefficients   Std Error      t Stat         P-value

  Intercept      9,177,092      500,022        18.4           1.93E--08

  HDD            3,638          1,755          2.1            6.81E--02

  CDD            17,223         1,424          12.1           7.21E--07

  R-squared:                    0.9722                        

  Adjusted                      0.9660                        
  r-squared:                                                  
  -------------- -------------- -------------- -------------- --------------

Table A.5. Regression analysis of post-retrofit monthly energy use in
North Fort

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      1,636,307      75,746         21.6           4.60E--09

  HDD            1,457          258            5.7            3.12E--04

  CDD            3,322          210            15.8           7.23E--08

  R-squared:                    0.9716                        

  Adjusted                      0.9653                        
  r-squared:                                                  
  -------------- -------------- -------------- -------------- --------------

Table A.6. Regression analysis of post-retrofit monthly energy use in
South Fort

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      8,376,563      246,991        33.9           8.31E--11

  HDD            2,249          840            2.7            2.53E--02

  CDD            13,475         686            19.6           1.07E--08

  R-squared:                    0.9859                        

  Adjusted                      0.9828                        
  r-squared:                                                  
  -------------- -------------- -------------- -------------- --------------

# Appendix B: Utility Bill Analysis to Determine Electricity Demand Savings

As one might expect, patterns of peak electrical demand were much more
difficult to understand than patterns of monthly electricity use. To get
a better idea of what was happening, we used all 18 months of available
pre-retrofit data and 24 months of post-retrofit data, instead of just
one year pre- and post-retrofit as we did with the energy use data.

The reason is that in the pre-retrofit period, billed peak demand in
both areas of Fort Polk depended on the season: For the most part, peak
monthly demand in November through February was a function of the
monthly low temperature, while in March through October peak monthly
demand was a function of the monthly high temperature. However, because
family housing made up 67% of the pre-retrofit electricity load in North
Fort (compared with only 37% in South Fort), the supplemental resistance
heating on the pre-retrofit heat pumps caused North Fort to have more
winter-peaking months than the South Fort. For example, in March 1994
demand in North Fort seemed to follow the pattern for a winter month,
while demand in South Fort followed the pattern of a summer month. In
February of 1995, North Fort also followed the winter pattern while
South Fort followed the summer pattern.

With only three or four heating months, one year's data was insufficient
to develop meaningful regressions. Thus Table B.1 presents the monthly
billed peak demand in Fort Polk's North Fort and South Fort areas for
the last 18 months of the pre-retrofit period, and Table B.2 presents
the peak demands for the first 24 months of post-retrofit period. The
tables include monthly high and low temperatures, and indicate for each
month whether the demand followed the winter or summer pattern. This
data was used to estimate demand savings.

Figure B.1 plots monthly peak demand for the South Fort, pre- and
post-retrofit. In the pre-retrofit period, peak demand was a linear
function of monthly high temperature during summer months and a linear
function of monthly low temperature in the winter months. In the
post-retrofit period, monthly peak demand is strictly a function of the
monthly high temperature. Clearly, the winter peaking was caused by
electric supplemental heating on the pre-retrofit heat pumps. Once the
heat pumps were replaced with GHPs (which have no supplemental heat) the
winter peak disappeared.

Figure B.2 plots pre- and post-retrofit monthly billed peak demand for
North Fort. With smaller electricity loads in this area the data shows
more scatter than that of the South Fort, but the pattern is still
clear. Note that the August 1993 peak demand of 9740 kW is an outlier.

Table B.1. Pre-retrofit monthly billed peak demand and monthly high and
low temperatures

  -------- ------------- -------- ----- ----------- -- -------- -------- -------- --------- -------- -- -------- -- --------- --
           Temperature                                 South                                North                             
           (°F)                                        Fort                                 Fort                              

                                                                                                                              

  Month    High                   Low                  Peak              Season             Peak                    Season    
                                                       demand                               demand                            
                                                       (kW)                                 (kW)                              

  Jun-93   96                     58                   30,072            Summer             5,920                   Summer    

  Jul-93   99                     71                   32,424            Summer             5,760                   Summer    

  Aug-93   101                    72                   33,399            Summer             9,740                   Summer    

  Sep-93   99                     51                   31,786            Summer             6,820                   Summer    

  Oct-93   89                     30                   26,107            Summer             5,040                   Summer    

  Nov-93   84                     29                   19,421            Winter             5,240                   Winter    

  Dec-93   75                     28                   20,496            Winter             5,200                   Winter    

  Jan-94   72                     21                   25,133            Winter             7,900                   Winter    

  Feb-94   78                     24                   23,923            Winter             7,020                   Winter    

  Mar-94   83                     32                   21,034            Summer             6,020                   Winter    

  Apr-94   87                     36                   25,805            Summer             5,240                   Summer    

  May-94   87                     53                   26,813            Summer             6,160                   Summer    

  Jun-94   94                     66                   30,778            Summer             6,920                   Summer    

  Jul-94   94                     63                   31,752            Summer             6,600                   Summer    

  Aug-94   93                     63                   30,576            Summer             6,700                   Summer    

  Sep-94   93                     48                   29,602            Summer             6,160                   Summer    

  Oct-94   91                     43                   26,712            Summer             5,160                   Summer    

  Nov-94   84                     44                   21,538            Summer             4,700                   Summer    

  Dec-94   78                     29                   21,336            Winter             5,520                   Winter    

  Jan-95   76                     25                   23,285            Winter             6,660                   Winter    

  Feb-95   78                     30                   22,075            Summer             6,600                   Winter    
  -------- ------------- -------- ----- ----------- -- -------- -------- -------- --------- -------- -- -------- -- --------- --

Table B.2. Post-retrofit monthly billed peak demand and monthly high and
low temperatures

  --------- ------------- ----------- --------- ----------- ---------- ---------
            Temperature               South                 North Fort 
            (°F)                      Fort                             

  Month     High          Low         Peak      Season      Peak       Season
                                      demand                demand     
                                      (kW)                  (kW)       

  Oct-96    86            39          20,899    Summer      4,540      Summer

  Nov-96    82            32          19,891    Summer      4,400      Summer

  Dec-96    79            19          17,808    Summer      4,500      Summer

  Jan-97    79            23          18,379    Summer      5,520      Summer

  Feb-97    81            32          17,775    Summer      4,440      Summer

  Mar-97    86            43          17,069    Summer      4,000      Summer

  Apr-97    88            39          20,227    Summer      4,160      Summer

  May-97    90            52          24,159    Summer      4,460      Summer

  Jun-97    93            59          25,872    Summer      5,900      Summer

  Jul-97    97            68          26,981    Summer      6,140      Summer

  Aug-97    97            63          27,048    Summer      6,260      Summer

  Sep-97    95            59          25,267    Summer      5,940      Summer

  Oct-97    90            39          23,285    Summer      5,260      Summer

  Nov-97    77            30          15,994    Summer      4,100      Summer

  Dec-97    73            28          16,968    Summer      4,320      Summer

  Jan-98    73            30          16,699    Summer      4,360      Summer

  Feb-98    73            34          16,263    Summer      4,160      Summer

  Mar-98    81            28          17,103    Summer      4,400      Summer

  Apr-98    82            43          19,522    Summer      4,080      Summer

  May-98    99            57          24,763    Summer      4,800      Summer

  Jun-98    99            59          27,351    Summer      6,520      Summer

  Jul-98    104           72          27,485    Summer      6,600      Summer

  Aug-98    104           70          27,519    Summer      6,560      Summer

  Sep-98    97            70          27,048    Summer      6,000      Summer
  --------- ------------- ----------- --------- ----------- ---------- ---------

![](media/image1.wmf){width="5.991666666666666in"
height="4.103472222222222in"}

![](media/image2.wmf){width="5.991666666666666in"
height="4.103472222222222in"}

**Figure B.2. North Fort billed monthly peak demand. Pre-retrofit demand
had winter and summer peaks, while post-retrofit peak demand is always a
function of monthly high temperature.**

To estimate peak demand savings in a typical year, we began by
correlating monthly billed peak demand with monthly low temperature for
pre-retrofit winter months, and with monthly high temperature for
pre-retrofit summer months and all post-retrofit months. The outlier in
Figure B.2 was omitted because, even if this was not a billing error,
omitting the outlier leads to a conservative estimate of peak demand
savings, and there is no plausible justification for attributing the
value to pre-retrofit housing as opposed to a one-month mission-related
anomaly. The regression equations are the following.

> [Pre-retrofit]{.underline}
>
> North Fort summer demand (kW) = 100.5 · T~max~ ­-- 3333.4 (B.1a)
>
> North Fort winter demand (kW) = --193.4 · T~min~ + 11,541 (B.1b)
>
> South Fort summer demand (kW) = 592.2 · T~max~ ­-- 25,976 (B.2a)
>
> South Fort winter demand (kW) = --644.9 · T~min~ + 39,032 (B.2b)
>
> [Post-retrofit]{.underline}
>
> North Fort demand (kW) = 75.6 · T~max~ ­-- 1571.4 (B.3)
>
> South Fort demand (kW) = 417.1 · T~max~ ­-- 14,829 (B.4)

In a typical year at Fort Polk, the annual low temperature is 19.9°F,
and the annual high is 100.9°F. Equations (B.1a) and (B.1b) show that in
the pre-retrofit period, the peak demand for North Fort would occur in
the winter, at 7692 kW compared with 6807 kW in the summer. However, the
overall pre-retrofit peak would occur in the summer when, according to
Eq. (B.2a), the demand in the South Fort is 33,777 kW. Combined with the
6807 kW in North Fort, annual peak demand in a typical year would be
40,584 kW.

The post-retrofit peak demand in the North Fort in a typical year is
6057 kW, and peak demand in South Fort is 27,256 kW, for a combined peak
of 33,313 kW. The demand savings for a typical year is then 40,584 --
33,313 = 7271 kW.

To estimate the uncertainty in the estimate of demand savings, we used a
bootstrap technique (Davison 1997). A 95% confidence interval for the
demand savings is 7.3 ± 3.1 MW.

Statistical analyses of Eqs. (B.1) through (B.4) are presented in tables
B.3 through B.8.

Table B.3. Regression analysis of North Fort pre-retrofit cooling peak
demand

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      --3333.4       3624.1         --0.92         0.3793

  Tmax           100.52         39.27          2.56           2.84E--02

  R-squared                     0.3958                        

  Adjusted                      0.3354                         
  r-squared                                                   
  -------------- -------------- -------------- -------------- --------------

Table B-4. Regression analysis of North Fort pre-retrofit heating peak
demand

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      11,541.3       1,991.3        5.80           0.0012

  Tmax           --193.44       72.52          --2.67         3.72E--02

  R-squared                     0.5425                        

  Adjusted                      0.4663                         
  r-squared                                                   
  -------------- -------------- -------------- -------------- --------------

Table B.5. Regression analysis of South Fort pre-retrofit cooling peak
demand

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      --25,976.2     5,297.6        --4.90         0.0003

  Tmax           592.19         57.95          10.22          1.40E--07

  R-squared                     0.8893                        

  Adjusted                      0.8808                         
  r-squared                                                   
  -------------- -------------- -------------- -------------- --------------

Table B.6. Regression analysis of South Fort pre-retrofit heating peak
demand

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      39,032.2       2,852.1        13.69          0.0002

  Tmax           --644.87       109.00         --5.92         4.09E--03

  R-squared                     0.8974                        

  Adjusted                      0.8718                         
  r-squared                                                   
  -------------- -------------- -------------- -------------- --------------

Table B.7. Regression analysis of North Fort post-retrofit peak demand

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      --1571.4       1072.8         --1.46         0.1571

  Tmax           75.57          12.20          6.20           3.09E--06

  R-squared                     0.6357                        

  Adjusted                      0.6192                         
  r-squared                                                   
  -------------- -------------- -------------- -------------- --------------

Table B.8. Regression analysis of South Fort post-retrofit peak demand

  -------------- -------------- -------------- -------------- --------------
  * *            Coefficients   Std Error      t Stat         P-value

  Intercept      --14,828.9     2,858.4        --5.19         3.35E--05

  Tmax           417.11         32.49          12.84          1.08E--11

  R-squared                     0.8822                        

  Adjusted                      0.8769                         
  r-squared                                                   
  -------------- -------------- -------------- -------------- --------------

# Appendix C: Analysis to Determine Persistence of Savings

The energy conservation measures installed in 1995 -- 1996 had a
definite impact on electricity use and demand at Fort Polk, shown
clearly in Figures 2 and 3 of the body of the report. But starting in
about August of 2000, total Fort Polk electricity use began a steady
rise, and by June 2003 the weather-normalized annual consumption was
about half way back to the where it was before the conservation measures
were installed. What happened? Was there a take-back effect in family
housing, or did this increase take place in the non-housing areas of
Fort Polk?

![](media/image3.wmf){width="5.995138888888889in"
height="4.095138888888889in"}At Fort Polk, electricity is supplied to
family housing through 16 separate electrical feeders. Each feeder
contains a submeter that the Army reads manually once per month to track
family housing electricity use. We obtained these manual readings for
the same period for which we obtained Fort Polk's utility bills, June
1993 to June 2003. Figure C-1 presents the sum of these monthly meter
readings for the 16 feeders. As with electricity use for the entire
facility, the raw data is not very informative. There seems to be a drop
in electricity use around the time the energy conservation measures were
installed, but the scatter in the data makes the reduction difficult to
quantify.

**Figure C-1. Monthly sums of readings from the 16 electric submeters in
the family housing areas of Fort Polk.**

![](media/image4.wmf){width="5.990972222222222in"
height="4.090277777777778in"}Figure C-2, which takes data from the 12
months ending with the graphed months and normalizes the data to a TMY,
makes it much clearer what has happened, at least initially. Annual
electricity use in family housing fell from about 77-79 million kWh per
year before the retrofits to about 51-53 million kWh per year
afterwards. It remained at this level for several years, but between
September 1999 and July 2000, energy use suddenly dropped by 21%, then
increased by about 41% over the next 14 months (this trough is visible
in Figure C-1 as well).

**Figure C-2. Annual electricity use in Fort Polk family housing. The
bars represent weather-normalized kWh for the 12-month period ending
with the graphed month.**

One factor that could have changed energy use in family housing is
demolition of housing units: Between September 1998 and August 2002, a
total of 362 older residences were demolished, leaving only 3641 of the
original 4003 units. About 10.4% of the original square footage of
housing was demolished, leaving 89.7%. But in Figure C-3 we overlay the
percentage of remaining housing square footage on the weather-normalized
manual meter readings. Obviously, demolition of housing units does not
account for what the data are showing. For this reason, we believe the
manual readings from the family housing meters are unreliable.

In our original study of the Fort Polk retrofit project, we attached
data loggers to 14 of the 16 family housing electric submeters in order
to read them electronically at 15-minute intervals. In July 2003, we
were able to rehabilitate 11 of our original 14 data loggers and began
collecting electric use data once again. To date the results have been
mixed. For example, Figure C-4 presents daily electricity use vs. daily
average temperature on

> ![](media/image5.wmf){width="5.375in" height="3.658333333333333in"}
> **Figure C-3. Weather-normalized total of manually read submeters in
> family housing, and percentage of original housing units remaining.
> Each bar represents kWh for the 12-month period ending with the
> graphed month.**

![](media/image6.wmf){width="5.625in" height="3.8534722222222224in"}

> **Figure C-4. Daily electricity use vs. daily average temperature for
> submetered Feeder 5, 1996-1997 and 2003-2004. Either this meter was
> not working correctly in 2003 -- 2004, or the feeder serves a
> different set of loads than it did in 1996 -- 1997.**

Feeder 5 from our original data collection effort from 1996 to 1997,
along with the more recent data. In 1996-1997, the data had the expected
pattern for electricity use in all-electric housing --- more energy was
used at the extreme temperatures in both summer (for cooling) and in
winter (for heating). But in the later data, the pattern seems to be
inverted --- less energy is used as outdoor air temperatures become more
extreme. Either this meter is no longer functioning properly, or the
electricity use is no longer limited to housing.

![](media/image7.wmf){width="5.991666666666666in"
height="4.103472222222222in"}Another example is presented in Figure C-5,
which plots daily energy use vs. daily average temperature for Feeder
14. Here at least the more recent data corresponds to what we expect for
a housing load, but the number of housing units served by this feeder
seems to have increased drastically. In 1996-1997, baseline energy use
(i.e., the portion unaffected by heating and cooling) was about 1800 kWh
per day, whereas in 2003-2004 it has increased to 5300 kWh per day. This
is nearly a 300% increase, and clearly much greater than one would
expect from an increase in electric appliances.

**Figure C-5. Daily energy use on Feeder 14 increased after 1996-1997 by
nearly 300% according to data gathered in 2003-2004, but this increase
is certainly due to an increase of housing units being served by the
feeder.**

Altogether, of the eleven feeders we rehabilitated in 2003, data from
seven are so different from the 1996-1997 data as to be unusable. On the
other hand, data from four of the eleven feeders (Feeders 3, 4, 6, and
16) were very similar to the 1996-1997 data, as can be seen in Figure
C-6. Coincidentally, there were no demolitions on these feeders, so
![](media/image8.wmf){width="7.0in" height="4.761111111111111in"}their
energy use is directly comparable.

**Figure C-6. Electricity use on four submetered feeders to Fort Polk
family housing appears to have changed very little, based on comparison
of 1996-1997 and 2003 -- 2004 data sets.**

We cannot be certain why the manual readings from the family housing
meters and the 15-minute-interval data from 7 of 11 data loggers would
be unreliable. However, we have a theory that explains what we see in
the data. Our theory, suggested by Figure C-2, is that electrical
distribution system circuits were switched in September 1999 and again
in July 2000, creating a period between these dates when housing
submeters did not capture all of the housing loads; and that after July
2000 large non-housing loads were being served through the housing
submeters. It is also possible that some of the housing submeters are no
longer functioning properly, especially since they are maintained by the
Army and not the utility. This theory would also explain why the use of
manual readings from the housing submeters as part of the M&V procedures
for the actual ESPC project was abandoned a few years into the project.

For each of the four feeders with usable data, we fit daily electricity
use data from 1996-1997 and 2003-2004 to a five-parameter function of
daily average temperature using the technique described in our 1998
evaluation of the Fort Polk project (Hughes and Shonder 1998). This
regression analysis allowed us to predict annual energy use for a
typical year. If there have been no increases in energy use, then the
TMY predictions from the two data sets should be roughly the same. Table
C-1 shows the results of the regression analysis of 1996-1997 and
2003-2004 electricity use data for the four feeders.

Table C-1. Annual electricity use predicted for a TMY by regression
analysis of 1996-1997 and 2003-2004 electricity use data for four
submetered Fort Polk family housing feeders.

  ------------------ ----------------- ------------------- ----------------
  Feeder             TMY energy use    TMY energy use      Percentage
                     based on          based on 2003-2004  change
                     1996-1997 data    data (kWh)          
                     (kWh)                                 

  3                  977,428           882,651             --9.7%

  4                  176,601           166,838             --5.5%

  6                  999,035           1,037,816           3.9%

  16                 4,763,891         4,982,995           4.6%

  Total              6,916,955         7,070,300           2.2%
  ------------------ ----------------- ------------------- ----------------

The analysis indicates that energy use on some of the feeders has
decreased, and on some it has increased. Some of the changes are
undoubtedly due to changes in occupancy, for which we have no
information. Overall, energy use for the four feeders has increased by
2.2% over 7 years. This is an annual rate of increase of just 0.3%.

Based on this analysis of a large sample of Fort Polk's housing, we
conclude that there have been only small increases in electricity use in
Fort Polk's family housing since the retrofits were installed. The 0.3%
annual increase is smaller than housing load growth predicted in the
1998 evaluation based on national averages at the time, for plug load
growth. Since in ESPC projects the ESCO is not accountable for plug load
growth, it follows that the ESPC energy savings have persisted.

# Appendix D: Utility Bill Analysis to Determine Electrical Cost Savings

In Appendix A we derived equations that predict pre- and post-retrofit
electrical use in the North and South Fort areas of Fort Polk given
base-65°F heating and cooling degree days. Subtracting the post-retrofit
electrical use from the pre-retrofit electrical use gives electrical
savings as a function of heating and cooling degree days:

[North Fort]{.underline}

> Monthly savings (kWh) = 75,722 + 372 · HDD + 444 · CDD (D.1)

[South Fort]{.underline}

> Monthly savings (kWh) = 800,529 + 1,389 · HDD + 3,748 · CDD (D.2)

Likewise, from Appendix B we can derive equations for monthly peak
demand savings as a function of monthly high and low temperatures:

[North Fort]{.underline}

> Summer demand savings (kW) = 24.96 · T~max~ -- 1,761.9 (D.3a)
>
> Winter demand savings (kW) = --75.57 · T~max~ -- 193.44 · T~min~ +
> 13,113 (D.3b)

[South Fort]{.underline}

> Summer demand savings (kW) = 175.08 · T~max~ -- 11,147 (D.4a)
>
> Winter demand savings (kW) = -- 417.11 · T~max~ -- 644.87 · T~min~ +
> 53,861 (D.4b)

Given these equations we can predict the demand and energy savings in
any given month knowing the base-65°F heating and cooling degree days
that occurred, and the monthly high and low temperature. This provides a
way of determining how much Fort Polk would have paid for electricity
had the project not been implemented. For each month in the
post-retrofit period, we estimate the energy and demand savings using
equations (D.1) through (D.4). Adding the estimated energy savings to
the actual billed energy use gives an estimate of what the energy use
would have been without the project. Likewise adding the estimated
demand savings to the actual billed peak demand gives an estimate of
what demand would have been without the project. Then given energy use
and demand without the project, we use the same rate schedule to
estimate what the electric bill would have been in that month.

## Electricity Rates

In the period from June 1993 to June 2003, Fort Polk's serving electric
utility has charged four different rates. These rates had two different
structures. The LGS rate structures in effect through October 2001
included declining block rates for both demand and energy. Consider for
example the LGS-15 rate in effect through June 1995. For demand, the
first block of 60 kW was billed at \$4.83 per kW, and the remaining
demand was billed at \$3.00 per kW. For energy, the first block of
30,000 kWh was billed at 0.0436 per kWh, the second block (up to 400
times the monthly peak demand) was billed at \$0.0341 per kWh, and the
remainder at \$0.0249 per kWh. The LGS-16 and LGS-17 rates were similar,
with slightly lower rates in all blocks.

In November 2001 Fort Polk was switched to the Small General Service
Rate (GS-1S), which is a declining block rate for energy only. First,
there is a customer charge of \$9.89 per month. The first block of
energy --- sized at 1575 kWh plus 55 times the peak demand --- is billed
at \$0.0918 per kWh; the second block, up to 24,500 kWh, is billed at
\$0.0476 per kWh. The charge for the remaining energy depends on the
season. From November through April, the rate is \$0.0288 per kWh, and
from May through October the rate is \$0.0335 per kWh.

Table D.1 presents the rates Fort Polk has paid and the periods during
which these rates were in effect. In addition to the rates, Fort Polk's
electricity bill depended on a number of riders as well. For example,
according to the utility's Rider G, energy and demand charges are
discounted by 5% in the South Fort bill because service is delivered at
a primary line voltage higher than 13,800 volts, and Fort Polk owns and
maintains all of the service transformers. Beginning in June 1996, a
"Formula Rate Plan" took effect, which provides a per-kWh discount that
varies from month to month.

Table D.1. Fort Polk Utility Rates

  --------- ----------- ---------- ---------- --------- --------- -----------------
  Rate      Effective   1st demand 2nd demand 1st       2nd       3rd energy
            date        charge,    charge,    energy    energy    charge, per kWh
                        per kW     per kW     charge,   charge,   
                                              per kWh   per kWh   

  LGS-15    June-93     \$4.83     \$3.00     \$.0436   \$.0341   \$.0250

  LGS-16    Jul-95      \$4.68     \$2.92     \$.0442   \$.0330   \$.0240

  LGS-17    Oct-95      \$4.62     \$2.87     \$.0417   \$.0326   \$.0239

  GS-1S     Nov-04      none       none       \$.0918   \$.0475   \$.0288/\$.0335
  --------- ----------- ---------- ---------- --------- --------- -----------------

Interestingly, a high portion of Fort Polk's electricity bill depends
not on the particular rate charged, but on the Fuel Cost Realignment
rider. This is a per-kWh charge applied monthly that is intended to
recover the utility's fuel costs. Over the 121 months of records
available, the fuel adjustment charge ranged from \$0.0125 to \$0.0540
per kWh. On average over this period, fuel adjustment costs accounted
for 45% of the total bills.

## An Example

During the month of September 1996 --- the first month after completion
of the energy conservation retrofits --- peak demand in the South Fort
was 25,301 kW, with 13,112,400 kWh consumed. Fort Polk was paying the
LGS-17 rate at the time. Table D.2 shows a breakdown of the bill for
that month.

Table D.1. Breakdown of Fort Polk utility bill for September 1996

  -------------------------- ----------------------------- --------------
  Charge                     Calculation                   Value

  First demand charge        \$4.62 × 60                   \$ 277.20

  Second demand charge       \$2.87 × (25,301 -- 60)       \$ 72,441.67

  First energy charge        \$0.0417×30,000               \$ 1,251.00

  Second energy charge       \$0.0326 × (400 × 25,301 --   \$ 328,947.04
                             30,000)                       

  Third energy charge        \$0.0239 × (13,112,400 -- 400 \$ 71,508.80
                             × 25,301)                     

  Subtotal, energy and                                     **\$
  demand                                                   474,425.71**

  Primary voltage discount   --0.05 × subtotal             \$ (23,721.29)

  Fuel adjustment cost       \$0.02493 × 13,112,400        \$ 326,892.13

  Formula rate reduction     --\$0.0001234 × 13,112,400    \$ (16,179.52)

  Total                                                    **\$
                                                           761,417.04**
  -------------------------- ----------------------------- --------------

Now, from weather records we find that the month of September 1996 had 5
heating degree days and 331 cooling degree days, and the high
temperature for the month was 91.4°F. From equation (C.2), the energy
savings during this month is estimated as

800,529 + (1,389)(5) + (3,748)(331) = 2,048,062 kWh .

Given that the actual electrical use for the month was 13,112,400 kWh,
we can estimate that if the project had not been installed, the
electrical use would have been 13,112,400 + 2,048,062 = 15,160,462 kWh.

From Eq. (D.4a) the demand savings during the month is estimated as

(175.08)(91.4) -- 11,147 = 4,855 kW .

So given that the actual peak demand was 25,301 kW, we can estimate that
had the energy conservation measures not been installed the peak demand
for this month would have been 25,301 + 4855 = 30,156 kW.

Now we use the same rates to calculate what the electrical bill would
have been with a peak demand of 30,156 kW and an electrical use of
15,160,462 kWh. The calculations are summarized in Table D.3.

Table D.2. Calculated Fort Polk electricity cost for September 1996
without savings

  -------------------------- ----------------------------- --------------
  First demand charge        \$4.62 × 60                   \$ 277.20

  Second demand charge       \$2.87 × (30,156 - 60)        \$ 86,375.52

  First energy charge        \$0.0417 × 30,000             \$ 1,251.00

  Second energy charge       \$0.0326 × (400 × 30,156 --   \$ 392,256.24
                             30,000)                       

  Third energy charge        \$0.0239 × (15,160,462 - 400  \$ 74,043.68
                             × 30,156)                     

  Subtotal, energy and                                     **\$
  demand                                                   554,203.64**

  Primary voltage discount   --0.05 × subtotal             \$ (27,710.18)

  Fuel adjustment cost       \$0.02493 × 15,160,462        \$ 377,950.32

  Formula rate reduction     --\$.0001234 × 15,160,462     \$ (18,706.65)

  Total                                                    **\$
                                                           885,737.13**
  -------------------------- ----------------------------- --------------

Now given the results of Table D.2 and D.3, we define the energy savings
in September 1996 to be \$885,737.13 -- \$761,417.04 = \$124,320.09.