EL25-015

The main stakeholders in the docket concerning Otter Tail Power Company's petition for approval of an electric service agreement for the Big Stone South Energy Storage Project, LLC (BSSEP) and associated tariff revisions (Docket No. EL25-015) are:

- Otter Tail Power Company (the utility proposing the agreement)
- Big Stone South Energy Storage Project, LLC (the customer/partner in the agreement)
- Poet Biorefining - Big Stone, LLC (an industrial end-user that will receive steam from BSSEP)
- South Dakota Public Utilities Commission (the regulatory body reviewing and approving the agreement)
- Commission staff and legal representatives
- No petitions to intervene or comments were filed by other parties or the public during the notice period

Positions:
- Otter Tail Power Company and Big Stone South Energy Storage Project, LLC are in favor of the proposed electric service agreement and associated tariff revisions.
- The South Dakota Public Utilities Commission reviewed and voted unanimously to approve the agreement and tariff revisions, indicating commission support.
- No parties or members of the public filed in opposition; there is no record of any stakeholder opposing the proposals in the docket 1, 1.

In summary, all identified stakeholders either supported or did not oppose the proposals, and the docket saw no formal opposition.

Key events and submissions in the Otter Tail Power Company (OTPCO) proceeding for approval of an electric service agreement (ESA) with Big Stone South Energy Storage Project, LLC (BSSEP) and associated tariff revisions are as follows:

- April 21, 2025: Otter Tail Power Company filed its petition and associated confidential materials with the South Dakota Public Utilities Commission (SDPUC) seeking approval of an ESA with deviations for BSSEP and associated tariff changes 1, 2.
- April 22, 2025: The filing was officially received by the Commission. Notices of the filing and intervention deadline were electronically transmitted to interested individuals and entities on the Commission's listserv on April 24, 2025 3, 3.
- May 9, 2025: Deadline for intervention or comments. No petitions to intervene or comments were filed 3, 3.
- May 14, 2025: SDPUC staff served the first set of data requests on the parties 2, 2.
- May 28-29, 2025: Otter Tail responded to staff data requests 3, 4.
- June 16, 2025: Staff served a second set of data requests on the parties 5.
- June 17, 2025: Otter Tail responded to data requests 3, 3.
- July 15, 2025: The Commission considered the matter at its regular meeting and voted unanimously to approve the ESA with deviations and associated tariff revisions 3, 3, 3.
- July 17, 2025: The Commission issued its order granting approval of the ESA with deviations and approving tariff revisions, effective August 1, 2025 3, 6, 3, 3, 3.
- July 23, 2025: Otter Tail filed a compliance filing with the final version of tariff section 16.00 reflecting commission-approved changes 7, 7.
- August 1, 2025: Effective date for the new electric service agreement and revised tariff sheets 6, 8, 8, 8, 1, 1.

Throughout the process, confidential treatment was requested for proprietary and sensitive information included in the filings 9, 9.

The primary area of growth identified in this docket is the addition of the Big Stone South Energy Storage Project, LLC (BSSEP), which is a new large load at a new location with an estimated partially controllable demand of 155,000 kW when operating at full capacity. The project involves a thermal storage facility that uses electricity to heat blocks of carbon and generate steam for use in an adjacent biofuels plant (POET Biorefining - Big Stone, LLC) 1, 1, 1.

Key considerations related to this growth include:

- Infrastructure Expansion: Otter Tail Power Company will serve BSSEP via new distribution assets, including two new transformers and two new sections of underground cable, independently connecting BSSEP and POET through the Big Stone South substation 1, 1, 1.
- Customer Impact: BSSEP is the only customer affected by this filing, and the new electric service agreement with deviations is specific to this project. There is no expected general rate increase or decrease for other customers 2, 2.
- Regulatory and Tariff Considerations: The electric service agreement has a 20-year term, includes protections for other customers and the company, and involves firm load service under the Large General Service tariff and non-firm load under a new Thermal Market Energy Pricing Rider. Key deviations have been filed confidentially 1, 1, 1.
- Confidential Information: Certain business details, pricing, and formula components are classified as trade secrets and are protected as confidential information under South Dakota law 3, 3.

In summary, the docket identifies significant growth through the integration of a new large industrial customer and energy storage project, with key considerations including infrastructure requirements, customer-specific impacts, regulatory compliance, and the protection of sensitive business information.

The provided excerpts do not directly discuss specific financial or timeline risks and concerns related to the docket for Otter Tail Power Company's electric service agreement with Big Stone South Energy Storage Project, LLC. The available information primarily addresses the approval process, tariff revisions, confidential treatment of sensitive information, and the effective date of the agreement.

However, some indirect observations can be made:
- The agreement is for a 20-year term with an effective date of August 1, 2025, and is described as having "protections for other customers and the company" 1.
- Key deviations from standard agreements, including pricing components and formulas, are confidential due to their proprietary and sensitive nature 2, 2.
- The company executed the agreement and sought approval to ensure it is reflected in the tariff summary, with Big Stone South Energy Storage Project, LLC being the only customer affected by this filing 3, 3.

No explicit financial or timeline risks or concerns are detailed in the available excerpts.

Docket EL25-015 concerns Otter Tail Power Company's petition to the South Dakota Public Utilities Commission (PUC) for approval of an electric service agreement (ESA) with deviations for the Big Stone South Energy Storage Project, LLC (BSSEP), as well as associated tariff revisions. The project involves serving BSSEP, a large new load with an estimated partially controllable demand of 155,000 kW, which will operate a thermal storage facility using electricity to heat carbon blocks. The generated steam will be supplied to a nearby biofuels company for industrial processes. Otter Tail will serve BSSEP via new distribution assets, including two transformers and underground cables.

The ESA has a 20-year term and specifies that BSSEP's firm load will be served under the Large General Service tariff (Schedule 10.04) and non-firm load under the new Thermal Market Energy Pricing Rider (Schedule 14.16). Key deviations from standard contracts are confidential. The PUC approved the ESA and tariff revisions as just and reasonable on July 17, 2025, with an effective date of August 1, 2025. BSSEP is the only customer affected by this filing. The final tariff changes are documented in Section 16.00 of Otter Tail's electric rate schedule 1, 2.