SCHEDULE 13G

CUSIP No.

87876P201

Names of Reporting Persons

Tryfon Natsis and Depoina Pantopoulou, as Joint Tenants with the Right of Survivorship

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

GREECE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 460,300.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 460,300.00

Aggregate Amount Beneficially Owned by Each Reporting Person

460,300.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

1.8 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person: Percent of class represented by amount in row (9) has been calculated based on 25,269,362 shares of Tecogen Inc. common stock outstanding as of May 20, 2025, as reported in Tecogen Inc.'s prospectus on Form 424B3 filed with the Securities and Exchange Commission on May 22, 2025.

SCHEDULE 13G

Item 1.

(a)

Name of issuer:

Tecogen Inc.

(b)

Address of issuer's principal executive offices:

76 Treble Cove Road, Building 1, North Billerica, Massachusetts, 01862

Item 2.

(a)

Name of person filing:

This statement is being filed by Tryfon Natsis and Despoina Pantopoulou, as spouses and Joint Tenants with the Right of Survivorship, as Reporting Persons.

(b)

Address or principal business office or, if none, residence:

The residential address for each Reporting Person is Block 7, The St. Regis Saadiyat Island Residences, Al Saadiyat Island, 54345 Abu Dhabi, United Arab Emirates.

(c)

Citizenship:

Each Reporting Person is a citizen of Greece.

(d)

Title of class of securities:

Common Stock, $0.001 par value

(e)

CUSIP No.:

87876P201

Item 3.

If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);

(b)

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);

(c)

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);

(d)

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);

(e)

An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f)

An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g)

A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h)

A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:

(k)

Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

Item 4.

Ownership

(a)

Amount beneficially owned:

460,300 shares of Tecogen Inc. common stock.

(b)

Percent of class:

1.8% (based on 25,269,362 shares of Tecogen Inc. common stock outstanding as of May 20, 2025, as reported in Tecogen Inc.'s prospectus on Form 424B3 filed with the Securities and Exchange Commission on May 22, 2025).

(c)

Number of shares as to which the person has:

(i) Sole power to vote or to direct the vote:

(ii) Shared power to vote or to direct the vote:

460,300

(iii) Sole power to dispose or to direct the disposition of:

(iv) Shared power to dispose or to direct the disposition of:

460,300

Item 5.

Ownership of 5 Percent or Less of a Class.

Ownership of 5 percent or less of a class

Item 6.

Ownership of more than 5 Percent on Behalf of Another Person.

Not Applicable

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.

Not Applicable

Item 8.

Identification and Classification of Members of the Group.

Not Applicable

Item 9.

Notice of Dissolution of Group.

Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Tryfon Natsis and Depoina Pantopoulou, as Joint Tenants with the Right of Survivorship

Signature:	/s/ Tryfon Natsis
Name/Title:	Tryfon Natsis, in his capacity as a Joint Tenant with the Right of Survivorship
Date:	08/14/2025

Signature:	/s/ Despoina Pantopoulou
Name/Title:	Despoina Pantopoulou, in her capacity as a Joint Tenant with the Right of Survivorship
Date:	08/14/2025