FORM 10-K (Mark One)☒ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Fiscal Year Ended December 31, 2025 Or ☐TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from _____ to _____ Commission File Number: 001-41306 ALTERNUS CLEAN ENERGY, INC.(Exact name of registrant as specified in its charter) 87-1431377 17 State Street, Suite 4000, New York, NY 10004(212) 739-0727(Address of principal executive offices) (Zip Code) Registrant’s telephone number, including area code: (212) 739-0727 Securities registered pursuant to Section 12(b) of the Act: None Securities registered pursuant to Section 12(g) of the Securities Exchange Act: Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.Yes☐No☒ Indicate by check mark if the registrant is not required to file reports pursuant to Section13 or Section15(d) of the Act.Yes☐No☒ Indicate by check mark whether the registrant (1)has filed all reports required to be filed by Section13 or 15(d) of the SecuritiesExchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file suchreports), and (2)has been subject to such filing requirements for the past 90 days.Yes☐No☒ Indicate by check mark whether the registrant has submitted electronically, every Interactive Data File required to be submittedpursuant to Rule405 of RegulationS-T (§232.405 of this chapter) during the preceding 12months (or for such shorter period thatthe registrant was required to submit such files).Yes☐No☒ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smallerreporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smallerreporting company,” and “emerging growth company, in Rule 12b-2 of the Exchange Act. LargeAccelerated Filer☐Non-Accelerated Filer☒Emerging Growth Company☒ AcceleratedFiler☐SmallerReportingCompany☒ Table of Contents If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period forcomplying with any new or revised financial accounting standards provided pursuant to Section13(a) of the Exchange Act.☐ Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of theeffectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C.7262(b)) bythe registered public accounting firm that prepared or issued its audit report.☐ If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of theregistrant included in the filing reflect the correction of an error to previously issued financial statements.☐ Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-basedcompensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b).☐ Indicate by check mark whether the registrant is a shell company (as defined in Rule12b-2 of the Act). Yes:☐No:☒ The aggregate market value of voting stock held by non-affiliates of the Registrant on June 30, 2025, based on the closing price of$6.40for shares of the Registrant’s common stock as reported by The OTCMarket, was approximately $1.65million. Shares ofcommon stock beneficially owned by each executive officer and director have been excluded in that such persons may be deemedto be affiliates. The number of shares outstanding of the Registrant’s common stock, par value $0.0001 per share, on June 12, 2026was 724,658. Documents Incorporated by Reference None Table of Contents PART I Item 1.BusinessItem 1A.Risk FactorsItem 1B.Unresolved Staff CommentsItem 1C.CybersecurityItem 2.PropertiesItem 3.Legal ProceedingsItem 4.Mine Safety Disclosures PART II Item 5.Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of EquitySecuritiesItem 6.[Reserved]Item 7.Management’s Discussion and Analysis of Financial Condition and Results of OperationsItem 7A.Quantitative and Qualitative Disclosures About Market RiskItem 8.Financial Statements and Supplementary DataItem 9.Changes in and Disagreements with Accountants on Accounting and Financial DisclosureItem 9A.Controls and ProceduresItem 9B.Other InformationItem 9C.Disclosure Regarding Foreign Jurisdictions that Prevent Inspections PART III Item 10.Directors, Executive Officers and Corporate GovernanceItem 11.Executive CompensationItem 12.Security Ownership of Certain Beneficial Owners and Management and Related Stockholder MattersItem 13.Certain Relationships and Related Transactions, and Director IndependenceItem 14.Principal Accountant F