# XcelEnergy

RESPONSIBLEBY 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)1in 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. Pleaseinclude 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%