Otter Tail Corp

CONDENSED NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (unaudited)

1. Summary of Significant Accounting Policies

Overview

Otter Tail Corporation (OTC) and its subsidiaries (collectively, the "Company", "us", "our" or "we") form a diverse, multi-platform business consisting of a vertically integrated, regulated utility with generation, transmission and distribution facilities complemented by manufacturing businesses providing metal fabrication for custom machine parts and metal components, manufacturing of extruded and thermoformed plastic products, and manufacturing of polyvinyl chloride (PVC) pipe products. We classify our business into three segments: Electric, Manufacturing and Plastics.

Basis of Presentation

The unaudited consolidated financial statements included herein have been prepared pursuant to the rules and regulations of the SEC for interim reporting. Accordingly, they do not include all the information and footnotes required by generally accepted accounting principles. In the opinion of management, we have included all adjustments, including normal recurring accruals, necessary for a fair presentation of the consolidated financial statements for the periods presented. The consolidated financial statements and condensed notes thereto should be read in conjunction with the consolidated financial statements and notes included in our Annual Report on Form 10-Kfor the fiscal year ended December 31, 2024.

Because of the seasonality of our businesses and other factors, earnings for the three and nine months ended September 30, 2025 should not be taken as an indication of earnings for all or any part of the balance of the current year or as an indication of earnings for future years.

Use of Estimates

We use estimates based on the best information available in recording transactions and balances resulting from business operations. As better information becomes available or actual amounts are known, the recorded estimates are revised. Consequently, operating results can be affected by revisions to prior accounting estimates.

Reclassifications

Short-term investments in the amount of $0.8 million were previously included in other current assets as of December 31, 2024. This amount has been reclassified to maintain consistency and comparability between the periods presented and are now presented separately on the consolidated balance sheets. The reclassification had no impact on previously reported current or total assets, current or total liabilities, or total shareholders' equity.

Recent Accounting Pronouncements

Income Taxes. In December 2023, the Financial Accounting Standards Board (FASB) issued amended authoritative guidance codified in Accounting Standards Codification (ASC) 740, Income Taxes. The amended guidance requires additional disaggregated information in effective tax rate reconciliation disclosures and additional disaggregated information about income taxes paid. The updated standard is effective for our annual periods beginning in 2025. The amended guidance is to be applied on a prospective basis with the option to apply the standard retrospectively. We anticipate adopting the updated standard in our Form 10-K for the year ending December 31, 2025, and electing to apply the standard on a retrospective basis for all periods presented.

Disaggregated Income Statement Expenses. In November 2024, the FASB issued authoritative guidance codified in ASC 220, Income Statement—Reporting Comprehensive Income, which will require additional disclosure of certain costs and expenses within the notes to the financial statements. The new standard is effective for our annual periods beginning in 2027 and interim periods beginning in the first quarter of fiscal 2028 and can be applied on either a prospective or retrospective basis. Early adoption of the new standard is permitted. We anticipate adopting the updated standard in our Form 10-K for the year ending December 31, 2027.

Measurement of Credit Losses. In July 2025, the FASB issued amended authoritative guidance codified in ASC 326, Financial Instruments - Credit Losses. The amended guidance provides a practical expedient permitting an entity to assume that conditions on the balance sheet date remain unchanged over the life of the asset when estimating expected credit losses for current accounts receivable and current contract assets. The updated standard is effective for our annual and interim periods beginning in 2026 and is to be applied on a prospective basis. We are currently evaluating the impact that the updated standard will have on our consolidated financial statements, but we do not anticipate it will have a material effect on our future financial position or operating results.

Software Costs. In September 2025, the FASB issued amended authoritative guidance codified in ASC 350, Intangibles – Goodwill and Other. The amended guidance updates the cost capitalization threshold for internal-use software development costs by removing all references to software project development stages and providing new guidance on how to evaluate whether the probable-to-complete recognition threshold has been met. The updated standard is effective for our annual and interim periods beginning in 2028. Early adoption of the amended guidance is permitted. The amended guidance can be applied on a prospective, modified, or retrospective basis. We are currently evaluating the impact that the updated standard will have on our consolidated financial statements, but we do not anticipate it will have a material effect on our future financial position or operating results.

2. Segment Information

Our business is comprised ofthree reportable segments: Electric, Manufacturing and Plastics, consistent with our business strategy, organizational structure, and internal reporting and review processes. Segment net income is the primary measure of segment profit or loss used by our chief operating decision maker in assessing segment performance and allocating resources to our segments.

Segment Profit or Loss

Information about each segment, including significant expenses and net income of each segment, for the three and nine months ended September 30, 2025 and 2024 are as follows:

Electric Segment

Manufacturing Segment

Plastics Segment

Capital Expenditures and Identifiable Assets

The following provides capital expenditures for each reportable segment and our corporate cost center for the nine months ended September 30, 2025 and 2024:

The following provides the identifiable assets by segment and corporate assets as of September 30, 2025 and December 31, 2024:

Corporate assets consist primarily of cash and cash equivalents, investments, and prepaid expenses.

Reconciliation to Consolidated Amounts

Certain costs are not allocated to our operating segments. Corporate operating costs include items such as corporate staff and overhead costs, the results of our captive insurance company and other items excluded from the measurement of operating segment performance. Corporate is not an operating segment, rather it is added to operating segment totals to reconcile to consolidated amounts.

Included below is a reconciliation of certain segment information and our unallocated corporate costs to consolidated amounts for the three and nine months ended September 30, 2025 and 2024:

3. Revenue

The following presents our operating revenues from external customers, in total and by amounts arising from contracts with customers and alternative revenue program (ARP) arrangements, disaggregated by revenue source and segment for the three and nine months ended September 30, 2025 and 2024:

4. Select Balance Sheet Information

Receivables and Allowance for Credit Losses

Receivables as of September 30, 2025 and December 31, 2024 are as follows:

The following is a summary of activity in the allowance for credit losses for the nine months ended September 30, 2025 and 2024:

Inventories

Inventories consist of the following as of September 30, 2025 and December 31, 2024:

Investments

The following is a summary of our investments as of September 30, 2025 and December 31, 2024:

Debt Securities. The following table summarizes the amortized cost and fair value of available-for-sale debt securities and the corresponding amounts of gross unrealized gains and losses as of September 30, 2025 and December 31, 2024:

As of September 30, 2025 and December 31, 2024, no unrealized losses on debt securities were deemed to be other-than-temporary.

The following table summarizes the fair value of available-for-sale debt securities by contractual maturity date as of September 30, 2025:

Equity Securities. The amount of net unrealized gains and losses during the nine months ended September 30, 2025 and 2024 on marketable equity securities still held as of September 30, 2025 and 2024 was not material.

Property, Plant and Equipment

Major classes of property, plant and equipment as of September 30, 2025 and December 31, 2024 include:

5. Regulatory Matters

Regulatory Assets and Liabilities

The following presents our current and long-term regulatory assets and liabilities as of September 30, 2025 and December 31, 2024 and the period we expect to recover or refund such amounts:

South Dakota Rate Case

On June 4, 2025, Otter Tail Power (OTP) filed a request with the South Dakota Public Utilities Commission (SDPUC) for an increase in revenue recoverable under general rates in South Dakota. In its filing, OTP requested a net increase in annual revenue of $5.7 million, or 12.50%, based on an allowed rate of return on rate base of 8.29% and an allowed rate of return on equity (ROE) of 10.80% on an equity ratio of 53.54% of total capital. Through this proceeding, OTP has proposed changes to the mechanism of certain cost and investment recovery, with recovery moving from riders into base rates. If the SDPUC does not issue its decision on OTP's request within 180 days, OTP can increase rates on an interim basis beginning December 1, 2025. These interim rate revenues, when collected, are subject to potential refund until the finalization of the rate case.

Minnesota Rate Case

On October 31, 2025, OTP filed a request with the Minnesota Public Utilities Commission (MPUC) for an increase in revenue recoverable under general rates in Minnesota. In its filing, OTP requested a net increase in annual revenue of $44.8 million, or 17.7%, based on an allowed rate of return on rate base of 7.92% and an allowed ROE of 10.65% on an equity ratio of 53.5% of total capital. The request includes, among other items, accelerated recovery of the remaining investment of the jurisdictionally allocated share of Coyote Station. The accelerated recovery request is equal to $4.3 million annually. The request is driven by the MPUC’s order in OTP’s most recent Integrated Resource Plan to discontinue serving Minnesota customers with capacity and energy from Coyote Station by December 2031. If this part of the request is granted, we anticipate the amounts collected would be deferred and recognized over the remaining estimated useful life of the plant, which extends until 2041.

The filing also included an interim rate request for a net increase in annual revenue of $31.8 million, or 12.6%. We anticipate interim rates will commence on January 1, 2026, and will be subject to potential refund until the finalization of the rate case.

6. Short-Term and Long-Term Borrowings

The following is a summary of our outstanding short- and long-term borrowings by borrower, OTC or OTP, as of September 30, 2025 and December 31, 2024:

Short-Term Debt

The following is a summary of our lines of credit as of September 30, 2025 and December 31, 2024:

Borrowings under each credit facility are subject to a variable rate of interest on outstanding balances and a commitment fee is charged based on the average unused amount available to be drawn under the respective facility. The variable rate of interest to be charged is based on a benchmark interest rate, either the Secured Overnight Financing Rate (SOFR) or a Base Rate, as defined in the credit agreements, selected by the borrower at the time of an advance, subject to the conditions of each agreement, plus an applicable credit spread. The credit spread ranges from zero to 2.00%, depending on the benchmark interest rate selected, and is subject to adjustment based on the credit ratings of the relevant borrower. There were no outstanding borrowings on either credit facility as of September 30, 2025. The weighted-average interest rate on all outstanding borrowings as of December 31, 2024 was 5.61%.

Long-Term Debt

The following is a summary of outstanding long-term debt by borrower as of September 30, 2025 and December 31, 2024:

On March 27, 2025, OTP entered into a Note Purchase Agreement pursuant to which OTP issued, in a private placement transaction, $100.0 million of senior unsecured notes consisting of (a) $50.0 million of 5.49% Series 2025A Senior Unsecured Notes due March 27, 2035, and (b) $50.0 million of 5.98% Series 2025B Senior Unsecured Notes due June 5, 2055. The Series 2025A Notes were issued on March 27, 2025, upon entering into the agreement. The Series 2025B Notes were issued on June 5, 2025.

Per the terms of the agreement, OTP may prepay all or any part of the notes (in an amount not less than 10% of the aggregate principal amount of the notes then outstanding in the case of a partial prepayment) at 100% of the principal amount so prepaid, together with unpaid accrued interest and a make-whole amount, as defined in the agreement; provided that no default or event of default exists under the agreement. Any prepayment of the Series 2025A Notes then outstanding on or after December 27, 2034, or the Series 2025B Notes then outstanding on or after December 5, 2054, will be made without any make-whole amount. Consistent with other of our borrowings, the agreement contains a number of restrictions on the business of OTP, including restrictions on OTP’s ability to merge, sell substantially all assets, create or incur liens on assets, guarantee the obligations of any other party, and engage in certain transactions with affiliates.

Financial Covenants

Certain of OTC's and OTP's short- and long-term debt agreements require the borrower, whether OTC or OTP, to maintain certain financial covenants, including a maximum debt to total capitalization ratio of 0.60 to 1.00 or 0.65 to 1.00, depending on the debt agreement, a minimum interest and dividend coverage ratio of 1.50 to 1.00, and a maximum level of priority indebtedness. As of September 30, 2025, OTC and OTP were in compliance with these financial covenants.

7. Employee Postretirement Benefits

Pension Plan and Other Postretirement Benefits

The Company sponsors a noncontributory funded pension plan (the Pension Plan), an unfunded, nonqualified Executive Survivor and Supplemental Retirement Plan (the ESSRP), both accounted for as defined benefit pension plans, and a postretirement healthcare plan accounted for as an other postretirement benefit plan.

The following tables include the components of net periodic benefit cost (income) related to our defined benefit pension plans and other postretirement benefits for the three and nine months ended September 30, 2025 and 2024:

The following table includes the impact of regulation on the recognition of periodic benefit cost (income) arising from pension and other postretirement benefits for the three and nine months ended September 30, 2025 and 2024:

We had no minimum funding requirements for our Pension Plan or any other postretirement benefit plans as of December 31, 2024. We didnot make any contributions to our Pension Plan during the nine months ended September 30, 2025 and 2024.

8. Income Taxes

The Company's effective tax rate was 14.1% and 17.9% for the three months ended September 30, 2025 and 2024 and 14.0% and 18.8% for the nine months ended September 30, 2025 and 2024. These rates differ from the federal statutory rate of 21% primarily due to the impact of production tax credits (PTCs) associated with the energy generation of our wind and solar assets, partially offset by the impact of state taxes. The decrease in our effective tax rate for each period was primarily driven by an increase in PTCs from our wind generation assets. In late 2024, we completed our first wind repowering project and additional projects were completed in 2025. The completion of these repowering projects resulted in the commencement of PTCs associated with the generation from the facilities.

One Big Beautiful Bill Act

On July 4, 2025, broad spending and tax law legislation referred to as the One Big Beautiful Bill Act (OBBBA) was enacted in the U.S. The aspects of the law that impact our financial position and may impact our future investment opportunities include certain changes to corporate income taxes and modifications to existing renewable energy credits.

The OBBBA includes changes to corporate income tax rules and regulations, including reinstating 100% bonus depreciation, immediate expensing of domestic research and development costs, and modifications to the business interest expense limitation.

The effects of changes in tax laws and regulations are required to be recognized in our consolidated financial statements in the period of enactment. Accordingly, as of September 30, 2025, we recognized a reduction to our current year income tax payable in the amount of $7.7 million, with a corresponding increase to our deferred income tax liability, as a result of electing to deduct previously deferred research and development costs in the current year. We also anticipate electing bonus depreciation for eligible assets in our 2025 corporate income tax return, which will result in a reduction of our current year income tax payable and an increase to our deferred income tax liability.

The OBBBA also alters the timing and eligibility of certain tax credits for renewable energy projects. Wind and solar projects that begin construction by July 4, 2026 are eligible for technology-neutral tax credits (production tax credits or investment tax credits). Projects that begin construction after July 4, 2026 must be in service by December 31, 2027 to qualify for technology-neutral tax credits. For projects that begin construction after December 31, 2025, new provisions restrict tax credit eligibility for those projects involving material assistance or effective control by a Foreign Entity of Concern, as defined in the legislation, which includes entities linked to China, Russia, Iran or North Korea.