v3.25.4
Cover - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Mar. 05, 2026
Jun. 30, 2025
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-40503    
Entity Registrant Name NET Power Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 98-1580612    
Entity Address, Address Line One 320 Roney St.    
Entity Address, Address Line Two Suite 200    
Entity Address, City or Town Durham    
Entity Address, State or Province NC    
Entity Address, Postal Zip Code 27701    
City Area Code (919)    
Local Phone Number 287-4750    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company true    
Entity Ex Transition Period false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 73.8
Documents Incorporated by Reference
DOCUMENTS INCORPORATED BY REFERENCE
Portions of the definitive Proxy Statement for the registrant’s 2026 Annual Meeting of Stockholders have been incorporated by reference into Part III of this Report.
    
Entity Central Index Key 0001845437    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false    
Class A Common Stock      
Document Information [Line Items]      
Title of 12(b) Security Class A Common Stock    
Trading Symbol NPWR    
Security Exchange Name NYSE    
Entity Common Stock, Shares Outstanding   84,687,931  
Warrants, each exercisable for one share of Class A Common Stock at a price of $11.50      
Document Information [Line Items]      
Title of 12(b) Security Warrants, each exercisable for one share ofClass A Common Stock at a price of $11.50    
Trading Symbol NPWR-WT    
Security Exchange Name NYSE    
Class B Common Stock      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   139,727,880