Attachment 1: Customer Notice Date of Notice: September 26, 2025     NOTICE OF FILING OF AMENDED TARIFF TO INCREASE THE DEMAND SIDE MANAGEMENT COST ADJUSTMENT (“DSMCA”) IN THE COLORADO P.U.C. NO. 11 ELECTRIC TARIFF of Black Hills Colorado Electric, LLC d/b/a Black Hills Energy     You are hereby notified that Black Hills Colorado Electric, LLC, d/b/a Black Hills Energy, 105 South Victoria Avenue, P.O. Box 75, Pueblo, Colorado, 81003-0075, has filed with the Public Utilities Commission of the State of Colorado (“Commission”), in accordance with the Public Utilities Law, an advice letter with revised tariff to amend its Demand Side Management Cost Adjustment (“DSMCA”) inputs on Tariff Sheet No. 71, in the Rates section of its Colo. P.U.C. No. 11-Electric Tariff, to become effective on January 1, 2026. The revised tariff will affect all retail customers subject to the DSMCA rate if the Commission allows the tariff to become effective.   The DSMCA rate is updated semi-annually (April and October) and is applicable to all retail customers. The principal purpose of this filing is to revise Black Hills’ DSMCA calculation inputs to reflect the approved budget for the 2026 DSM Plan Period and to update the forecasted sales revenue for calendar year 2025. The DSMCA rate is calculated to recover, among other things, the approved DSM budget over twelve consecutive billing months.   This DSMCA filing includes the approved budget from Proceeding No. 24A-0157E of $7,377,449 for Demand Side Management Program (DSMP) costs for calendar year 2026. This resulting 3.18% DSMCA rate is an increase of 0.25% from the existing DSMCA rate of 2.93% approved in Proceeding No. 25AL-0141E.   If permitted to go into effect on January 1, 2026, the tariff revisions will result in a decrease of annual revenues of approximately $4,318. Based on the proposed rate increase, the average residential customer monthly bill, under Rate Schedule RS-1 with typical usage of 600 kWh per month, will increase $0.30 from $124.54 to $124.84, or 0.24%. The average small commercial customer monthly bill, under Rate Schedule SGS-N with typical usage of 2,300 kWh per month, will increase $0.99 from $417.14 to $418.13, or 0.24%. Large commercial and industrial customers may call Black Hills Energy at (719)-546-6410 to obtain information concerning how the requested tariff amendments may affect them.   Copies of the proposed and present tariffs as filed with the Commission are available for inspection at the public offices of Black Hills Energy at 105 South Victoria Avenue, Pueblo, Colorado, 81003; or, at the office of the Commission, 1560 Broadway, Suite 250, Denver, Colorado 80202. Customers with questions concerning the proposed or present tariffs may call the Commission at (303) 894-2000; or, may contact Black Hills Energy by telephone at (888) 890-5554 or by email customerservice@support.blackhillsenergy.com. In addition, the Company’s proposed and present tariffs may be viewed at www.blackhillsenergy.com and the applicable Colorado statutes and Commission rules may be viewed at https://puc.colorado.gov.   Any person may file written comments or objections concerning the filing, with the Commission, 1560 Broadway, Suite 250, Denver, Colorado, 80202, at the following website: https://puc.colorado.gov/how-to-participate. Requests for written notices can also be made to the Commission by telephone at (303) 894-2000 or, alternatively, by contacting the Consumer Affairs section of the Commission at its local number (303) 894-2070 or toll-free number (800) 456-0858. The Commission will consider all written comments and objections submitted prior to the evidentiary hearing on the application. Written objections (protests) must be filed at least ten (10) days before the proposed effective date of January 1, 2026. Filing a written objection (protest) by itself will not allow you to participate as a party in any proceeding established in these matters. If you wish to participate as a party in this matter, you must file written intervention documents under Commission Rule 723-1-1401, 4 Colorado Code of Regulations 723-1.   The rates, rules, and regulations ultimately authorized by the Commission may or may not be the same as those proposed and may include rates higher or lower than those proposed or currently in effect.   The Commission may suspend the proposed tariffs, rates, rules, or regulations. The Commission may hold a hearing to determine which rates, rules, and regulations will be authorized. If a hearing is held, any member of the public may attend the hearing and may make a statement under oath about the proposed tariffs, whether or not he or she has filed an objection or intervention. If the filing is uncontested or unopposed, the Commission may determine the matter without a hearing and without further notice.       By: Dan Ahrens Manager, Regulatory