# EDGAR Filing Document

**Accession Number:** 0002074096
**File Stem:** 0001537435-25-000064
**Filing Date:** 2025-6
**Character Count:** 7465
**Document Hash:** fcb72cde74c803ebc8bdd9e715cdfee4
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001537435-25-000064.hdr.sgml**: 20250624

**ACCESSION NUMBER**: 0001537435-25-000064

**CONFORMED SUBMISSION TYPE**: 4

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20250303

**FILED AS OF DATE**: 20250624

**DATE AS OF CHANGE**: 20250624

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** Lafaille Stephen
- **CENTRAL INDEX KEY:** 0002074096

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 4
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-36103
- **FILM NUMBER:** 251070278

**MAIL ADDRESS:**
- **STREET 1:** 76 TREBLE COVE ROAD
- **CITY:** NORTH BILLERICA
- **STATE:** MA
- **ZIP:** 01862
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** TECOGEN INC.
- **CENTRAL INDEX KEY:** 0001537435
- **STANDARD INDUSTRIAL CLASSIFICATION:** AIR COND & WARM AIR HEATING EQUIP & COMM & INDL REFRIG EQUIP [3585]
- **ORGANIZATION NAME:** 06 Technology
- **EIN:** 043536131
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 76 TREBLE COVE ROAD
- **STREET 2:** BLDG. 1
- **CITY:** NORTH BILLERICA
- **STATE:** MA
- **ZIP:** 01862
- **BUSINESS PHONE:** 781-466-6400

**MAIL ADDRESS:**
- **STREET 1:** 76 TREBLE COVE ROAD
- **STREET 2:** BLDG. 1
- **CITY:** NORTH BILLERICA
- **STATE:** MA
- **ZIP:** 01862

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** TECOGEN INC
- **DATE OF NAME CHANGE:** 20111215

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## FORM 4

### STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

[ ] Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

---

| | | |
|:---|:---|:---|
| **1. Name and Address of Reporting Person**<sup>*</sup><br>Lafaille Stephen<br><sub>(Last) (First) (Middle)</sub><br>76 TREBLE COVE ROAD<br><sub>(Street)</sub><br>NORTH BILLERICA, MA 01862<br><sub>(City) (State) (Zip)</sub> | **3. Date of Earliest Transaction (Month/Day/Year)**<br>2025-03-03 | **5. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[ ] Director [ ] 10% Owner<br>[X] Officer (give title below) [ ] Other (specify below)<br>_VP of Business Development_ |
| **2. Issuer Name and Ticker or Trading Symbol**<br>TECOGEN INC. [ TGEN ] | **4. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | 3. Transaction Code (V) | 3. Transaction Code (V) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | Code | V | Amount | (A) or (D) | Price | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| Common Stock | 2025-03-03 |  | P |  | 400 | A | $2.50 | 400 | D |  |
| Common Stock | 2025-06-03 |  | X |  | 10000 | A | 0.71<sup>(1)</sup> | 10400 | D |  |
| Common Stock | 2025-06-03 |  | S |  | 10000 | D | 4.88<sup>(2)</sup> | 400 | D |  |
| Common Stock | 2025-06-04 |  | X |  | 15000 | A | 0.71<sup>(1)</sup> | 15400 | D |  |
| Common Stock | 2025-06-04 |  | S |  | 15000 | D | 5<sup>(3)</sup> | 400 | D |  |
| Common Stock | 2025-06-06 |  | X |  | 25000 | A | 1.10<sup>(4)</sup> | 25400 | D |  |
| Common Stock | 2025-06-06 |  | S |  | 25000 | D | 5.98<sup>(5)</sup> | 400 | D |  |
| Common Stock | 2025-06-23 |  | X |  | 10000 | A | 1.10<sup>(4)</sup> | 10400 | D |  |
| Common Stock | 2025-06-23 |  | S |  | 10000 | D | $7.25 | 400 | D |  |

---

## Table II - Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | 4. Transaction Code (V) | 4. Transaction Code (V) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 6. Date Exercisable and Expiration Date | 6. Date Exercisable and Expiration Date | 7. Title and Amount of Underlying Securities | 7. Title and Amount of Underlying Securities | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| Stock Options (Right to Buy) | $0.71 | 2025-06-03 |  | X |  |  | 10000 | <sup>(6)</sup> | 2030-07-09 | Common Stock | 50000 | $0.71 | 40000 | D |  |
| Stock Options (Right to Buy) | $0.71 | 2025-06-04 |  | X |  |  | 15000 | <sup>(6)</sup> | 2030-07-09 | Common Stock | 40000 | $0.71 | 25000 | D |  |
| Stock Options (Right to Buy) | $1.10 | 2025-06-06 |  | X |  |  | 25000 | 2023-01-21<sup>(7)</sup> | 2032-01-21 | Common Stock | 52500 | $1.10 | 27500 | D |  |
| Stock Options (Right to Buy) | $1.10 | 2025-06-23 |  | X |  |  | 10000 | 2023-01-21<sup>(7)</sup> | 2032-01-21 | Common Stock | 25000 | $1.10 | 17500 | D |  |

---

### Footnotes:

(1) Shares acquired pursuant to exercise of Stock Option Agreement dated 7/9/2020

(2) Multiple share sales between $4.75 and $5.25 per share

(3) 10,000 shares sold for $4.90 per share, and 5,000 shares sold for $5.10 per share

(4) Shares acquired pursuant to stock option agreement dated 1/21/2022

(5) Multiple share sales between $5.85 and $6.10

(6) Vests 50% upon achievement of Adjusted EBITDA goal of 2% of revenue in two consecutive quarters, and 50% upon achievement of Adjusted EBITDA goal of 3% of revenue in four consecutive quarters

(7) Vests 50% per year

**Signature:** /s/ Stephen Lafaille  
**Date:** 2025-06-24

### Remarks:

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

**Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.**