Summary of Significant Accounting Policies and Other Information (Policies)	9 Months Ended
Sep. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation	The condensed consolidated financial statements include the accounts of Power Solutions International, Inc. and its wholly-owned subsidiaries and majority-owned subsidiaries in which the Company exercises control. The condensed consolidated financial statements were prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and rules and regulations of the SEC for interim financial reporting. All intercompany balances and transactions have been eliminated in consolidation.
Basis of Presentation	Certain information and note disclosures normally included in the Company’s annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with the instructions to Form 10-Q and Article 8 of Regulation S-X and include all of the information and disclosures required by U.S GAAP for interim financial reporting. These unaudited Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements of the Company and related footnotes for the year ended December 31, 2024, included in the 2024 Annual Report on Form 10-K, filed with the SEC on March 24, 2025 (the “2024 Annual Report”). The Company’s significant accounting policies are described in the aforementioned 2024 Annual Report. The accompanying interim financial information is unaudited; however, the Company believes the financial information reflects all adjustments (consisting of items of a normal recurring nature) necessary for a fair presentation of its financial position, results of operations and cash flows in conformity with U.S. GAAP. Operating results for interim periods are not necessarily indicative of annual operating results.
Segments	Segments The Company operates as one business and geographic operating segment. Operating segments are defined as components of a business that can earn revenues and incur expenses for which discrete financial information is available that is evaluated on a regular basis by the chief operating decision maker (“CODM”). The Company’s CODM is its principal executive officer, who decides how to allocate resources and assess performance. A single management team reports to the CODM, who manages the entire business. The Company’s CODM reviews consolidated statements of income to make decisions, allocate resources and assess performance, and the CODM does not evaluate the profit or loss from any separate geography or product line.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires that management make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions include the valuation of allowances for credit losses, inventory reserves, warranty reserves, stock-based compensation, evaluation of goodwill, other intangibles, property, plant and equipment for impairment, income tax valuation allowances and determination of useful lives of long-lived assets. Actual results could materially differ from those estimates.
Restricted Cash	Restricted Cash Restricted cash consists of funds that are contractually restricted as to usage or withdrawal due to required minimum levels of cash collateral for letters of credits and contractual agreements with customers.
Inventories	Inventories The Company’s inventories consist primarily of engines and parts. Engines are valued at the lower of cost, including estimated freight-in, or net realizable value. Parts are valued at the lower of cost or net realizable value, except for integral parts provided by customers for installation on custom ordered engines. Such parts are accounted for as noncash consideration which is valued at fair value. Net realizable value approximates replacement cost. Cost is principally determined using the first-in, first-out method and includes material, labor and manufacturing overhead. It is the Company’s policy to review inventories on a continuing basis for obsolete, excess and slow-moving items and to record valuation adjustments for such items in order to eliminate non-recoverable costs from inventory. Valuation adjustments are recorded in an inventory reserve account and reduce the cost basis of the inventory in the period in which the reduced valuation is determined. Inventory reserves are established based on quantities on hand, usage and sales history, customer orders, projected demand and utilization within a current or future power system. Specific analysis of individual items or groups of items is performed based on these same criteria, as well as on changes in market conditions or any other identified conditions.
Warranty Costs	Warranty Costs The Company offers a standard limited warranty on the workmanship of its products that in most cases covers defects for a defined period. Warranties for certified emission products are mandated by the U.S. Environmental Protection Agency (the “EPA”) and/or the California Air Resources Board (the “CARB”) and are longer than the Company’s standard warranty on certain emission-related products. The Company’s products also carry limited warranties from suppliers. The Company’s warranties generally apply to engines fully manufactured by the Company and to the modifications the Company makes to supplier base products. Costs related to supplier warranty claims are generally borne by the supplier and passed through to the end customer. Warranty estimates are based on historical experience and represent the projected cost associated with the product. A liability and related expense are recognized at the time products are sold. The Company adjusts estimates when it is determined that actual costs may differ from initial or previous estimates. The Company’s warranty liability is generally affected by failure rates, repair costs and the timing of failures. Future events and circumstances related to these factors could materially change the estimates and require adjustments to the warranty liability. In addition, new product launches require a greater use of judgment in developing estimates until historical experience becomes available.
Recently Issued Accounting Pronouncements - Adopted and Recently Issued Accounting Pronouncements – Not Yet Adopted	Recently Issued Accounting Pronouncements – Adopted In November 2023, the FASB issued ASU 2023-07, Improvements to Reportable Segment Disclosures – Segment Reporting (Topic 280). The amendments to this standard require public entities to disclose more detailed information about their reportable segments’ significant expenses on an interim and annual basis. The amendments to this standard do not change how a public entity identifies its operating segments, aggregates those operating segments, or applies the quantitative thresholds to determine its reportable segments. The amendments to this standard apply to all public entities that are required to report segment information in accordance with Topic 280, Segment Reporting and are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The Company adopted this guidance for the year ending December 31, 2024 and subsequent interim periods. See Note 15. Segment Reporting for the new disclosures required by the standard. Recently Issued Accounting Pronouncements – Not Yet Adopted In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures - Income Taxes (Topic 740). The amendments to this standard enhances the transparency and decision usefulness of income tax disclosures, primarily related to rate reconciliation and income taxes paid information as well as effectiveness of overall income tax disclosures. The new standard is effective for non-public companies, and public business entities that meet the definition of a smaller reporting company as defined by the SEC, for annual periods beginning after December 15, 2024. The Company is required to adopt the guidance for its 2025 annual report filed on Form 10-K, though early adoption is permitted. The Company is currently evaluating the impact of these amendments on its disclosures, but this standard update will not impact the Company's results of operations or financial position. In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income: Expense Disaggregation Disclosures (Subtopic 220-40). This update requires entities to provide more detailed disclosures about the components of significant expense categories, enhancing the transparency and decision usefulness of financial statements. The amendments in this update are intended to provide investors with additional information about specific expense categories in the notes to the financial statements at interim and annual reporting periods. The updated standard is effective for annual periods beginning after December 15, 2026, and interim reporting periods thereafter, although early adoption is permitted. While we anticipate that the adoption of this standard will require additional disclosures, the Company is currently assessing the impact of the amendment to this standard on its consolidated financial statements. In July 2025, the FASB issued ASU 2025-05, Financial Instruments - Credit Losses: Measurement of Credit Losses for Accounts Receivable and Contract Assets (Topic 326). The update permits entities to elect a practical expedient for estimating expected credit losses on current trade receivables and current contract assets by assuming that conditions existing at the balance sheet date will remain unchanged over the life of those assets. The update standard is effective for fiscal years beginning after December 15, 2025, including interim periods within those fiscal years, with early adoption permitted. The Company is currently assessing the impact of the amendment to this standard on its consolidated financial statements.
Fair Value of Financial Instruments	Current Assets Cash and cash equivalents (Level 1) are measured at carrying value, which approximates fair value because of the short-term maturities of these instruments. Debt The Company measured its material debt obligations and notes payable at original carrying value. The fair value of the Revolving Credit Agreement and other short-term financing approximated carrying value, as it consisted primarily of variable rate loans. The Company measured its non-interest bearing note payable using a rate which the Company could obtain financing of similar nature from other sources at the date of the transaction.

Summary of Significant Accounting Policies and Other Information (Policies)

9 Months Ended

Sep. 30, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The condensed consolidated financial statements include the accounts of Power Solutions International, Inc. and its wholly-owned subsidiaries and majority-owned subsidiaries in which the Company exercises control. The condensed consolidated financial statements were prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and rules and regulations of the SEC for interim financial reporting. All intercompany balances and transactions have been eliminated in consolidation.

Basis of Presentation

Certain information and note disclosures normally included in the Company’s annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with the instructions to Form 10-Q and Article 8 of Regulation S-X and include all of the information and disclosures required by U.S GAAP for interim financial reporting. These unaudited Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements of the Company and related footnotes for the year ended December 31, 2024, included in the 2024 Annual Report on Form 10-K, filed with the SEC on March 24, 2025 (the “2024 Annual Report”). The Company’s significant accounting policies are described in the aforementioned 2024 Annual Report. The accompanying interim financial information is unaudited; however, the Company believes the financial information reflects all adjustments (consisting of items of a normal recurring nature) necessary for a fair presentation of its financial position, results of operations and cash flows in conformity with U.S. GAAP. Operating results for interim periods are not necessarily indicative of annual operating results.

Segments

The Company operates as one business and geographic operating segment. Operating segments are defined as components of a business that can earn revenues and incur expenses for which discrete financial information is available that is evaluated on a regular basis by the chief operating decision maker (“CODM”). The Company’s CODM is its principal executive officer, who decides how to allocate resources and assess performance. A single management team reports to the CODM, who manages the entire business. The Company’s CODM reviews consolidated statements of income to make decisions, allocate resources and assess performance, and the CODM does not evaluate the profit or loss from any separate geography or product line.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires that management make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions include the valuation of allowances for credit losses, inventory reserves, warranty reserves, stock-based compensation, evaluation of goodwill, other intangibles, property, plant and equipment for impairment, income tax valuation allowances and determination of useful lives of long-lived assets. Actual results could materially differ from those estimates.

Restricted Cash

Restricted cash consists of funds that are contractually restricted as to usage or withdrawal due to required minimum levels of cash collateral for letters of credits and contractual agreements with customers.

Inventories

The Company’s inventories consist primarily of engines and parts. Engines are valued at the lower of cost, including estimated freight-in, or net realizable value. Parts are valued at the lower of cost or net realizable value, except for integral parts provided by customers for installation on custom ordered engines. Such parts are accounted for as noncash consideration which is valued at fair value. Net realizable value approximates replacement cost. Cost is principally determined using the first-in, first-out method and includes material, labor and manufacturing overhead. It is the Company’s policy to review inventories on a continuing basis for obsolete, excess and slow-moving items and to record valuation adjustments for such items in order to eliminate non-recoverable costs from inventory. Valuation adjustments are recorded in an inventory reserve account and reduce the cost basis of the inventory in the period in which the reduced valuation is determined. Inventory reserves are established based on quantities on hand, usage and sales history, customer orders, projected demand and utilization within a current or

future power system. Specific analysis of individual items or groups of items is performed based on these same criteria, as well as on changes in market conditions or any other identified conditions.

Warranty Costs

The Company offers a standard limited warranty on the workmanship of its products that in most cases covers defects for a defined period. Warranties for certified emission products are mandated by the U.S. Environmental Protection Agency (the “EPA”) and/or the California Air Resources Board (the “CARB”) and are longer than the Company’s standard warranty on

certain emission-related products. The Company’s products also carry limited warranties from suppliers. The Company’s warranties generally apply to engines fully manufactured by the Company and to the modifications the Company makes to supplier base products. Costs related to supplier warranty claims are generally borne by the supplier and passed through to the end customer.

Warranty estimates are based on historical experience and represent the projected cost associated with the product. A liability and related expense are recognized at the time products are sold. The Company adjusts estimates when it is determined that actual costs may differ from initial or previous estimates. The Company’s warranty liability is generally affected by failure rates, repair costs and the timing of failures. Future events and circumstances related to these factors could materially change the estimates and require adjustments to the warranty liability. In addition, new product launches require a greater use of judgment in developing estimates until historical experience becomes available.

Recently Issued Accounting Pronouncements - Adopted and Recently Issued Accounting Pronouncements – Not Yet Adopted

Recently Issued Accounting Pronouncements – Adopted

In November 2023, the FASB issued ASU 2023-07, Improvements to Reportable Segment Disclosures – Segment Reporting (Topic 280). The amendments to this standard require public entities to disclose more detailed information about their reportable segments’ significant expenses on an interim and annual basis. The amendments to this standard do not change how a public entity identifies its operating segments, aggregates those operating segments, or applies the quantitative thresholds to determine its reportable segments. The amendments to this standard apply to all public entities that are required to report segment information in accordance with Topic 280, Segment Reporting and are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The Company adopted this guidance for the year ending December 31, 2024 and subsequent interim periods. See Note 15. Segment Reporting for the new disclosures required by the standard.

Recently Issued Accounting Pronouncements – Not Yet Adopted

In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures - Income Taxes (Topic 740). The amendments to this standard enhances the transparency and decision usefulness of income tax disclosures, primarily related to rate reconciliation and income taxes paid information as well as effectiveness of overall income tax disclosures. The new standard is effective for non-public companies, and public business entities that meet the definition of a smaller reporting company as defined by the SEC, for annual periods beginning after December 15, 2024. The Company is required to adopt the guidance for its 2025 annual report filed on Form 10-K, though early adoption is permitted. The Company is currently evaluating the impact of these amendments on its disclosures, but this standard update will not impact the Company's results of operations or financial position.

In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income: Expense Disaggregation Disclosures (Subtopic 220-40). This update requires entities to provide more detailed disclosures about the components of significant expense categories, enhancing the transparency and decision usefulness of financial statements. The amendments in this update are intended to provide investors with additional information about specific expense categories in the notes to the financial statements at interim and annual reporting periods. The updated standard is effective for annual periods beginning after December 15, 2026, and interim reporting periods thereafter, although early adoption is permitted.

While we anticipate that the adoption of this standard will require additional disclosures, the Company is currently assessing the impact of the amendment to this standard on its consolidated financial statements.

In July 2025, the FASB issued ASU 2025-05, Financial Instruments - Credit Losses: Measurement of Credit Losses for Accounts Receivable and Contract Assets (Topic 326). The update permits entities to elect a practical expedient for estimating expected credit losses on current trade receivables and current contract assets by assuming that conditions existing at the balance sheet date will remain unchanged over the life of those assets. The update standard is effective for fiscal years beginning after December 15, 2025, including interim periods within those fiscal years, with early adoption permitted. The Company is currently assessing the impact of the amendment to this standard on its consolidated financial statements.

Fair Value of Financial Instruments

Current Assets

Cash and cash equivalents (Level 1) are measured at carrying value, which approximates fair value because of the short-term maturities of these instruments.

Debt

The Company measured its material debt obligations and notes payable at original carrying value. The fair value of the Revolving Credit Agreement and other short-term financing approximated carrying value, as it consisted primarily of variable rate loans. The Company measured its non-interest bearing note payable using a rate which the Company could obtain financing of similar nature from other sources at the date of the transaction.