XcelEnergy

RESPONSIBLE BY NAYBRETM

Frank P. Prager

Vice President

Environmental Policy & Services

1800 Larimer St. Suite 1600

Denver, CO 80202

(303)294-2108

Janua~ 18,2011

Jeb Stenhouse

Chief, Program Development Branch

Clean Air Markets Division

Environmental Protection Agency

Office of Air and Radiation

1200 Pennsylvania Avenue

Washington, DC 20460

Southwestern Public Service Company Supplemental Comments Regarding

Revisions to Federal Implementation Plans to Reduce Interstate Transport of

Fine Particulate Matter and Ozone

Docket No. EPA-HQ-OAR-2009-0491

Dear Jeb:

Last week at your request, we discussed the comments filed by Southwestern

Public Service Company (SPS)1 in the above captioned docket on November 22, 2011.

You and your team had questions about the "must run" analysis included in the SPS

comments and described in detail in Exhibit C to the SPS comments.

As indicated in our November 22 comments, SPS derived Exhibit C through the

use of its ProSym system planning model. Table 1 to Exhibit C provided the modeled

capacity factors of the "must run" electric generating units on the SPS. SPS derived

Table 1 by setting the modeled price of imported power to zero. Under this scenario,

the ProSym model allows us to identify those units that must run regardless of cost to

meet load and address the constraints in the SPS transmission system.

Table 1 showed only the model results for units with projected capacity factors

that exceed those identified in EPA’s IPM model results. In our discussion last week,

you asked for the modeled capacity factors for all units on the SPS system under this

scenario. Per your request, attached is an updated table (labeled Table 1-Revised)

showing the modeled capacity factors for all SPS electric generating units.

As you review these data, please keep in mind a couple of constraints in the SPS

system that affect the results:

1 SPS is a subsidiary of Xcel Energy Inc.
Many of the SPS units are gas boilers of an older design. We are required to

maintain a minimum temperature on these boilers to ensure that they can be

available when we need them. We have programmed ProSym to ensure that it

recognizes that these boilers have minimum operating and startup times.

Because they are required to run in this manner, we cannot take 100% of market

purchases outside of SPS during off-peak hours.

Both units at one of our coal-fired power plants (Tolk) have lower capacity factors

in 2012 because the model includes a five week outage on each unit that we

planned to use to install Iow-NOx burners. The capacity factor would be higher

on these units without those planned outages.

The modeled capacity factors for the Harrington and Tolk coal-fired units are

slightly lower than they would be under a real world scenario. The assumption of

zero cost for imported power caused some imported power to offset a portion of

the electric production from these units in the model.

I hope the information in the attached responds to your questions. Please

include this letter and the attachment in the administrative record for the abovecaptioned docket. As always, feel free to contact me if you have any questions.

Sincerely,

Vice President,

Environmental Policy and Services

Xcel Energy Inc.
Table t - Revised

Owned and purchased

Plant

Name

Capacity Factor

Annual Xcel

Xcel EPA Ozone

Season

EPA

Ozone

Season

Blackhawk 2

Cunningham 2

Cunningham 4

Harrington 2

Massengale

Jones 2

Maddox 1

Moore Count

Nichols 2

X1

X3

LPCC 2xl

Tolk 2

Cooke ST 2

85% 7%

37% 14%

6% 1%

80% 85%

85% 6%

50% 13%

37% 0%

19% 0%

45% 14%

23% 0%

20% 0%

69% 91%

72% 79%

17% 0%

84% 14%

47% 32%

5% 1%

78% 85%

114% 13%

57% 32%

46% 25%

46% 0%

49% 32%

30% 0%

30% 0%

73% 88%

67% 81%

18% 0%