| Line Item | Jun 30, 2026 | Dec 31, 2025 | Sep 30, 2025 | Jun 30, 2025 | Mar 31, 2025 | Dec 31, 2024 | Sep 30, 2024 | Jun 30, 2024 | Mar 31, 2024 | Sep 30, 2023 | Jun 7, 2023 | Mar 31, 2023 | Dec 31, 2022 | Sep 30, 2022 | Jun 30, 2022 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Operating expenses | |||||||||||||||
| General and administrative | |||||||||||||||
| Sales and marketing | |||||||||||||||
| Research and development | |||||||||||||||
| Project development | |||||||||||||||
| Impairment and other charges | |||||||||||||||
| Depreciation, amortization, and accretion | |||||||||||||||
| Total operating expenses | |||||||||||||||
| Operating loss | |||||||||||||||
| Other income | |||||||||||||||
| Interest income, net | |||||||||||||||
| Change in Earnout Shares liability and Warrant liability | |||||||||||||||
| Change in Tax Receivable Agreement liability | |||||||||||||||
| Other income | |||||||||||||||
| Net other income | |||||||||||||||
| Net loss before income tax | |||||||||||||||
| Net loss after income tax | |||||||||||||||
| Net loss attributable to non-controlling interests | |||||||||||||||
| Net loss attributable to NET Power Inc. | |||||||||||||||
| Comprehensive loss attributable to non-controlling interests | |||||||||||||||
| Comprehensive loss attributable to NET Power Inc. | |||||||||||||||
| Loss per share attributable to shareholders, basic (in dollars per share) | |||||||||||||||
| Loss per share attributable to shareholders, diluted (in dollars per share) |