Marc Horstman - 04 Nov 2026 Form 4 Insider Report for Net Power Inc. (NPWR)

Reporting relationship: President and COO
Issuer ticker: NPWR
Reported as of: 04 Nov 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 06 Nov 2026, 18:12:04 UTC
Prior SEC filing: 04 Jun 2025
Source filing: View source filing
Reporting owner signature: /s/ Marc Horstman

Filing notes and source

Key filing fact

Marc Horstman filed Form 4 for Net Power Inc. (NPWR) on 06 Nov 2026.

Key facts

This page summarizes Marc Horstman's Form 4 filing for Net Power Inc. (NPWR).
2 reported transactions and 2 derivative rows are listed below.
Accepted by SEC: 06 Nov 2026, 18:12.

Change

Previous filing in this sequence was filed on 04 Jun 2025.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0002070734 Primary reporting owner

Horstman Marc

Relationship: President and COO
Address: C/O NET POWER INC., 11700 KATY FREEWAY, SUITE 700, HOUSTON
Signature: /s/ Marc Horstman
Signature date: 06 Nov 2026

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

NPWR transaction Derivative

Stock Options

Disposed to Issuer

Transaction value
Shares: -240,000
Change %: -100%
Price: $0.000000^*
Shares after: 0
Date: 04 Nov 2026
Ownership: Direct
Underlying class: Class A Common Stock
Underlying amount: 240,000
Exercise price: $2.13
Footnotes: F1, F2

NPWR transaction Derivative

Stock Options

Award

Transaction value
Shares: +240,000
Change %
Price: $0.000000^*
Shares after: 240,000
Date: 04 Nov 2026
Ownership: Direct
Underlying class: Class A Common Stock
Underlying amount: 240,000
Exercise price: $2.13
Footnotes: F1, F2

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 2 footnotes

Footnote F1

On November 4, 2026, the Issuer's board of directors approved an amendment to the stock option granted to the reporting person on June 2, 2025, which extends the period during which the vested option may be exercised following certain terminations of service. The amendment did not change the number of shares subject to the option, its exercise price, its vesting date or its expiration date, and the reporting person paid no consideration for it. The amendment is reported as the deemed cancellation of the original option and the grant of the amended option, each of which is exempt under Rule 16b-3.

Footnote F2

The option became exercisable in full on June 2, 2026.