Exhibit 99.1

Power Solutions International Announces Fourth Quarter and Full Year 2021 Financial Results

WOOD DALE, Ill., March 31, 2022 — Power Solutions International, Inc. (the “Company” or “PSI”) (OTC Pink: PSIX), a leader in the design, engineering and manufacture of emission-certified engines and power systems, announced fourth quarter and full year 2021 financial results.

Fourth Quarter 2021 Results

Sales for the fourth quarter of 2021 were $127.0 million, an increase of $22.0 million, or 21%, versus the comparable period last year. The improvement in sales is comprised of increases of approximately $8.3 million, $7.9 million, and $5.8 million in the transportation, industrial and power systems (formerly energy) end markets, respectively. Higher transportation end market sales were primarily driven by increased sales in the medium duty truck market due to the continued sell down and exhaustion of certain 6.0L engines that were previously prepaid by a customer under a long-term supply agreement, coupled with higher sales in the school bus market. The increased sales within the industrial end market primarily reflect increased demand for products used in the material handling/forklift markets. Higher power systems end market (formerly known as the energy end market) sales were driven by increased demand for the Company’s power generation products, especially for demand response products.

Gross profit decreased by $9.1 million, or 49%, in the fourth quarter of 2021 compared to the same period last year. Gross margin in the fourth quarter of 2021 was 7.6% versus 17.9% last year, primarily due to higher warranty costs, higher freight costs, material cost increases, and higher tariff costs, partly mitigated by the impact of higher sales, among other items. For the fourth quarter of 2021, warranty costs were $8.0 million, an increase of $6.7 million compared to warranty costs of $1.3 million last year, due largely to higher charges for adjustments to preexisting warranties and lower recognized recoveries during the fourth quarter of 2021. A majority of the warranty costs are attributable to products sold within the transportation end market.

Operating expenses decreased by $5.0 million, or 25%, versus the comparable period in 2020, due to lower selling, general and administrative (“SG&A”) costs of $3.3 million partly attributable to lower legal costs related to the Company’s indemnification obligations of former officers and employees driven largely by the conclusion of the United States Attorney’s Office for the Northern District of Illinois’ (“USAO”) trial involving former officers and employees during September 2021. Also, the Company

experienced lower wages and benefits expense in the fourth quarter of 2021 versus the prior year due largely to reduced incentive compensation incurred in the fourth quarter of 2021. Lower SG&A expenses in the fourth quarter of 2021 were partly mitigated by higher severance costs during the fourth quarter of 2021 driven by rightsizing activities. Lastly, lower operating expenses included reduced research, development and engineering expenses of $1.6 million, or 25%, from last year primarily as a result of lower project activity, coupled with lower wages and benefits driven by reduced headcount.

Net loss in the fourth quarter of 2021 was $7.6 million, or a loss of $0.33 per share, versus a net loss of $3.1 million, or $0.13 per share for the comparable prior year period. Adjusted net loss was $5.7 million, or Adjusted loss per share of $0.25, versus Adjusted net income of $1.1 million, or Adjusted earnings per share of $0.05 for the fourth quarter of 2020. Adjusted earnings before interest, taxes, depreciation and amortization (“EBITDA”) was a loss of $1.9 million compared to Adjusted EBITDA of $4.7 million in the fourth quarter last year.

See “Non-GAAP Financial Measures” below for the Company’s definition of total Adjusted net income (loss), Adjusted earnings (loss) per share, EBITDA and Adjusted EBITDA and the financial tables that accompany this release for reconciliations of these measures to their closest comparable GAAP measures.

Debt and Liquidity

The Company’s total debt was approximately $181 million at December 31, 2021, while cash and cash equivalents were approximately $6 million. This compares to total debt of approximately $156 million and cash and cash equivalents of approximately $5 million at September 30, 2021. Included in the Company’s total debt at December 31, 2021 were borrowings of $130 million under the Uncommitted Revolving Credit Agreement with Standard Chartered Bank (the “Credit Agreement”), and borrowings of $25 million and $25 million under the Second and Third Shareholder’s Loan Agreements with Weichai America Corp. (“Weichai”), its majority stockholder, respectively. The Credit Agreement included financial covenants which were effective for the Company during the three months ended December 31, 2021, including an interest coverage ratio and a minimum EBITDA threshold, as further defined in the Credit Agreement. For the three months ended December 31, 2021, the Company did not meet these covenants. On March 25, 2022, in connection with the extension of the Credit Agreement, the Company entered into a waiver with Standard Chartered, which waived the financial covenant defaults for the quarter ended December 31, 2021. No additional fee was incurred with this waiver.

On March 25, 2022, PSI entered into an amended $130.0 million Credit Agreement (the “Second Amended and Restated Credit Agreement”) with Standard Chartered Bank, which among other items, extends the maturity date of loans outstanding under the Company’s previous Credit Agreement to the earlier of March 24, 2023 or the demand of Standard Chartered. In connection with the Second Amended and Restated Credit Agreement, on March 25, 2022, the Company also amended two of its three separate shareholder’s loan agreements with its majority stockholder, Weichai America Corp. (“Weichai”), to among other things, extend the maturities thereof. Additional details are available in the Company’s Form 8-K filed on March 28, 2022.

Outlook for 2022

The Company expects its sales in 2022 to increase by at least 3% versus 2021 levels, a result of expectations for strong growth in the industrial and power systems end markets, partly mitigated by a reduction in sales in the transportation end market. Gross profit as a percentage of sales is targeted to improve by at least 5 percentage points in 2022, a function of lower warranty expense, pricing actions, improved cost recovery and cost savings initiatives. Notwithstanding this outlook, which is being driven in part by expectations for an improvement in supply chain dynamics, including timelier availability of parts, and a continuation of favorable economic conditions within the United States and across the Company’s various markets, the Company cautions that significant uncertainty remains as a result of supply chain challenges, inflationary costs, commodity volatility, and the COVID-19 pandemic, among other factors.

reduction in sales in the transportation end market. Gross profit as a percentage of sales is targeted to improve by at least 5 percentage points in 2022, a function of higher sales, lower warranty expense, pricing actions and improved mix, improved cost recovery and cost savings initiatives. Further, the Company anticipates that its expenses related to governmental investigations and other legal matters are likely to decline as the USAO’s trial involving former officers and employees concluded during September 2021. However, some uncertainty still exists as the Securities and Exchange Commission matter involving former officers and employees remains outstanding. Notwithstanding this outlook, which is being driven in part by expectations for an improvement in supply chain dynamics, including timelier availability of parts, and a continuation of favorable economic conditions within the United States and across the Company’s various markets, the Company cautions that significant uncertainty remains as a result of supply chain challenges, inflationary costs, commodity volatility, impact on the global economy of the war in Ukraine and the COVID-19 pandemic, among other factors.

Management Comments

Lance Arnett, chief executive officer, commented, “Increased demand from our customers across all end markets contributed to strong sales growth in the fourth quarter despite continued supply chain challenges that impacted our ability to timely meet certain orders. Higher material and shipping costs, among other factors, have also continued to impact our profitability despite higher sales. We’re not pleased with our financial results and we continue to take action to drive improvements.”

Arnett added, “To this end, we’ve taken significant actions to implement an improved supply chain and operations planning process to drive lower inventory, improve productivity and better our on-time delivery to customers. Also, during 2021 we took several steps to improve our cost structure through rightsizing initiatives, which when coupled with attrition contributed to the elimination of approximately 100 positions, or 12.5% of our total headcount. We also continue to review our facilities footprint in light of anticipated growth and efficiency gains. To date, this review resulted in the exit and sublease of a materials and warehousing facility which is expected to generate savings of approximately $0.9 million in 2022.”

Arnett continued, “As we enter 2022, we believe that demand from our customers remains favorable. We’re also optimistic that the steps we’ve taken to improve our operations and profitability will yield improved financial results during the year.”

About Power Solutions International, Inc.

Power Solutions International, Inc. (PSI) is a leader in the design, engineering and manufacture of a broad range of advanced, emission-certified engines and power systems. PSI provides integrated turnkey solutions to leading global original equipment manufacturers and end-user customers within the power systems, industrial and transportation end markets. The Company’s unique in-house design, prototyping, engineering and testing capabilities allow PSI to customize clean, high-performance engines using a fuel agnostic strategy to run on a wide variety of fuels, including natural gas, propane, gasoline, diesel and biofuels.

PSI develops and delivers complete power systems that are used worldwide in stationary and mobile power generation applications supporting standby, prime, demand response, microgrid, and co-generation power (CHP) applications; and industrial applications that include forklifts, agricultural and turf, arbor

care, industrial sweepers, aerial lifts, irrigation pumps, ground support, and construction equipment. In addition, PSI develops and delivers powertrains purpose-built for medium-duty trucks and buses including school and transit buses, work trucks, terminal tractors, and various other vocational vehicles. For more information on PSI, visit www.psiengines.com.

Cautionary Note Regarding Forward-Looking Statements

This press release contains forward-looking statements regarding the current expectations of the Company about its prospects and opportunities. These forward-looking statements are entitled to the safe-harbor provisions of Section 21E of the Securities Exchange Act of 1934. The Company has tried to identify these forward-looking statements by using words such as “anticipate,” “believe,” “budgeted,” “contemplate,” “estimate,” “expect,” “forecast,” “guidance,” “may,” “outlook,” “plan,” “projection,” “should,” “target,” “will,” “would,” or similar expressions, but these words are not the exclusive means for identifying such statements. These statements are subject to a number of risks, uncertainties, and assumptions that may cause actual results, performance or achievements to be materially different from those expressed in, or implied by, such statements.

The Company cautions that the risks, uncertainties and other factors that could cause its actual results to differ materially from those expressed in, or implied by, the forward-looking statements, include, without limitation: the impact of the ongoing COVID-19 pandemic could have on the Company’s business and financial results; the Company’s ability to continue as a going concern; the Company’s ability to raise additional capital when needed and its liquidity; uncertainties around the Company’s ability to meet funding conditions under its financing arrangements and access to capital thereunder; the potential acceleration of the maturity at any time of the loans under the Company’s uncommitted senior secured revolving credit facility through the exercise by Standard Chartered Bank of its demand right; the timing of completion of steps to address, and the inability to address and remedy, material weaknesses; the identification of additional material weaknesses or significant deficiencies; risks related to complying with the terms and conditions of the settlements with the Securities and Exchange Commission (the “SEC”) and the United States Attorney’s Office for the Northern District of Illinois (the “USAO”); variances in non-recurring expenses; risks relating to the substantial costs and diversion of personnel’s attention and resources deployed to address the internal control matters; the Company’s obligations to indemnify past and present directors and officers and certain current and former employees with respect to the investigations conducted by the SEC and the criminal division of the USAO, which will be funded by the Company with its existing cash resources due to the exhaustion of its historical primary directors’ and officers’ insurance coverage; the ability of the Company to accurately forecast sales, and the extent to which sales result in recorded revenues; changes in customer demand for the Company’s products; volatility in oil and gas prices; the impact of U.S. tariffs on imports from China on the Company’s supply chain; impact on the global economy of the war in Ukraine; disruptions to the Company’s supply chain; the impact of increasing warranty costs and the Company’s ability to mitigate such costs; any delays and challenges in recruiting key employees consistent with the Company’s plans; any negative impacts from delisting of the Company’s common stock par value $0.001 from the NASDAQ Stock Market and any delays and challenges in obtaining a re-listing on a stock exchange; and the risks and uncertainties described in reports filed by the Company with the SEC, including without limitation its Annual Report on Form 10-K for the fiscal year ended December 31, 2021 and the Company’s subsequent filings with the SEC.

The Company’s forward-looking statements are presented as of the date hereof. Except as required by law, the Company expressly disclaims any intention or obligation to revise or update any forward-looking statements, whether as a result of new information, future events or otherwise.

Contact:

Power Solutions International, Inc.

Philip Kranz

Director of Investor Relations

(630) 509-6470

Philip.Kranz@psiengines.com

Results of operations for the three and twelve months ended December 31, 2021 compared with the three and twelve months ended December 31, 2020 (UNAUDITED):

NM    Not meaningful

POWER SOLUTIONS INTERNATIONAL, INC.

CONSOLIDATED BALANCE SHEETS

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POWER SOLUTIONS INTERNATIONAL, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

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Non-GAAP Financial Measures

In addition to the results provided in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) above, this press release also includes non-GAAP (adjusted) financial measures. Non-GAAP financial measures provide insight into selected financial information and should be evaluated in the context in which they are presented. These non-GAAP financial measures have limitations as analytical tools and should not be considered in isolation from, or as a substitute for, financial information presented in compliance with U.S. GAAP, and non-GAAP financial measures as reported by the Company may not be comparable to similarly titled amounts reported by other companies. The non-GAAP financial measures should be considered in conjunction with the consolidated financial statements, including the related notes, and Management’s Discussion and Analysis of Financial Condition and Results of Operations included in the Company’s Form 10-K for the year ended December 31, 2021. Management does not use these non-GAAP financial measures for any purpose other than the reasons stated below.

The Company believes that Adjusted net income (loss), Adjusted earnings (loss) per share, EBITDA, and Adjusted EBITDA provide relevant and useful information, which is widely used by analysts, investors and competitors in its industry as well as by the Company’s management in assessing the performance of the Company. Adjusted net income (loss) is defined as net income (loss) as adjusted for certain items that the Company believes are not indicative of its ongoing operating performance. Adjusted earnings (loss) per share is a measure of the Company’s diluted earnings (loss) per common share adjusted for the impact of special items. EBITDA provides the Company with an understanding of earnings before the impact of investing and financing charges and income taxes. Adjusted EBITDA further excludes the effects of other non-cash charges and certain other items that do not reflect the ordinary earnings of the Company’s operations.

Adjusted net income (loss), Adjusted earnings (loss) per share, EBITDA, and Adjusted EBITDA are used by management for various purposes, including as a measure of performance of the Company’s operations and as a basis for strategic planning and forecasting. Adjusted net income (loss), Adjusted earnings (loss) per share, and Adjusted EBITDA may be useful to an investor because these measures are widely used to evaluate companies’ operating performance without regard to items excluded from the calculation of such measures, which can vary substantially from company to company depending on the accounting methods, the book value of assets, the capital structure and the method by which the assets were acquired, among other factors. They are not, however, intended as alternative measures of operating results or cash flow from operations as determined in accordance with U.S. GAAP.

The following table presents a reconciliation from Net loss to Adjusted net (loss) earnings for the three and twelve months ended December 31, 2021 and 2020 (UNAUDITED):

The following table presents a reconciliation from Loss per common share – diluted to Adjusted (loss) earnings per share for the three and twelve months ended December 31, 2021 and 2020 (UNAUDITED):

The following table presents a reconciliation from Net loss to EBITDA and Adjusted EBITDA for the three and twelve months ended December 31, 2021 and 2020 (UNAUDITED):