Southwestern Public Service Company Attachment O - Transmission Formula Rate 2016 True-Up Customer Meeting July 13, 2017

Table of Contents - Notebook Tab 1 – 2016 True-Up Tab 2 – Variance Analyses and Capital Additions Tab 3 – Disclosure of Material Changes Tab 4 – Supporting Documentation Tab 5 – Radial Line Study (RLS)

Purpose of Meeting Review Attachment O 2016 True-Up Adjustment Primary Drivers of 2016 Estimated vs. Actual Review Schedule 1 True-Up Adjustment Material Changes, Supporting Documentation, RLS Customer Questions

Southwestern Public Service Company Summary of Attachment O True-Up Adjustment January 1, 2016 – December 31, 2016 Actual 2016 ATRR $ 264,109,742 Projected 2016 ATRR $ 266,501,009 ATRR Adjustment ($ 2,391,268) 2016 Actual BPU Revenue Adjustment ($ 9,612,361) 2016 Actual ATRR Volume Adjustment $ 9,189,612 Net True-Up – Over recovery without interest ($ 2,814,017)

Projected Zonal Rate per kW-yr $ 27.1080 Southwestern Public Service Company Summary of Attachment O True-Up – Divisor January 1, 2016 – December 31, 2016 Projected 2016 Divisor 4,808,000 kW Actual 2016 Divisor 4,469,000 kW Volume Adjustment 339,000 kW Projected Zonal Rate per kW-yr $ 27.1080 Volume Revenue Adjustment1 $9,189,612 1 (339,000) * $27.1080 = $9,189,612

Southwestern Public Service Company Cost Drivers – Decrease in Actual 2016 ATRR from the Estimated 2016 ATRR Projected 2016 ATRR $266.5M 2016 Actual Cost Drivers: Rate Base and Cost of Capital ($ 6.3) Revenue Credits $ 7.3 O&M Expense ($ .4) Depreciation Expense ($ 1.4) Taxes ($ 1.5) 2016 Actual ATRR $264.1M

Southwestern Public Service Company Rate Base Change Actual vs Southwestern Public Service Company Rate Base Change Actual vs. Projected Transmission Net Plant In Service – Decrease ($ 33.9M) General & Intangible Net Plant in Service – Decrease ($ 1.9M) Total Net Plant In Service Decrease ($ 35.8M) Adjustments to Rate Base Increase in ADIT Credit Adjustment to Rate Base ($ 38.3M) Working Capital & Land Held for Future Use ($ 0.2M) Actual Net Decrease in Rate Base from Projected ($ 74.3M)

Southwestern Public Service Company Cost of Capital Changes – Actual vs. Projected Ratios Actual Projected Difference Long Term Debt 45.93% 46.38% (0.45%) Equity 54.07% 53.62% 0.45% Cost Long Term Debt 5.50% 5.58% (0.08%) Equity 10.50% 10.50% 0.00% Weighted Cost Long Term Debt 2.53% 2.59% (0.06%) Equity 5.68% 5.63% 0.05% Total 8.21% 8.22% (0.01%) Rate Base $1,575.3M $1,649.6M $( 74.3M) Return on Rate Base $ 129.3M $ 135.6M $( 6.3M)

Southwestern Public Service Company Base Plan Upgrade Projects Revenue Requirements Projected BPU Revenue Requirement $134,110,705 Change in Carrying Charge (11.34% vs. 11.46%) $ 1,285,166 Change in Plant In Service $ 8,327,195 Actual BPU Revenue Requirement $143,723,066 *WsP BPU – Table 36 of template

Southwestern Public Service Company Radial Line Study 2016 Update Radial Line Gross Plant Investment in 2016 Estimate $ 71.4M Changes in Gross Plant Balances for Existing Radial Lines $ 10.8M New Radial Lines $ 3.5M Radial Line Investment in 2016 Actual $ 85.7M

Projected 2016 Schedule 1 ARR $ 4,511,876 Southwestern Public Service Company Summary of Schedule 1 True-Up Adjustment January 1, 2016 – December 31, 2016 Actual 2016 Schedule 1 ARR $ 3,956,899 Projected 2016 Schedule 1 ARR $ 4,511,876 ARR Adjustment ($ 554,977) 2016 Actual Schedule 1 Volume Adjustment1 $ 318,121 Net True-Up – Over recovery without interest ($ 236,856) 1 339,000 * $0.9384 = $318,121