Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Current assets
Cash and cash equivalents	$ 133,146	$ 199,430
Investments in securities, available-for-sale	174,867	138,462
Interest receivable	845	1,376
Prepaid expenses and other current assets	2,202	4,496
Total current assets	311,060	343,764
Long-term assets
Restricted cash	1,203	2,427
Investments in securities, available-for-sale	10,280	38,242
Intangible assets, net	179,058	181,572
Property, plant, and equipment, net	40,561	32,758
Operating lease right-of-use assets	514	551
Other long-term assets	146	387
Total assets	542,822	599,701
Current liabilities
Accounts payable	346	1,437
Accrued liabilities	4,438	7,565
Due to related parties	7,110	37,262
Operating lease liabilities, current portion	1,082	1,074
Finance lease liabilities, current portion	81	127
Total current liabilities	13,057	47,465
Warrant liability	5,816	10,850
Asset retirement obligation	3,685	3,597
Non-current operating lease liabilities	2,387	2,584
Total liabilities	24,945	64,496
Commitments and contingencies (Note 14)
Mezzanine shareholders' equity
Redeemable non-controlling interests in subsidiary	312,552	331,301
Shareholders' equity
Preferred Stock, $.0001 par value; 1,000 shares authorized; no shares issued or outstanding as of March 31, 2026 and December 31, 2025	0	0
Additional paid-in capital	909,830	898,425
Accumulated other comprehensive loss	1	129
Accumulated deficit	(704,529)	(694,672)
Total shareholders' equity	205,325	203,904
Total liabilities, mezzanine shareholders' equity, and shareholders' equity	542,822	599,701
Class A Common Stock
Shareholders' equity
Common stock, value, issued	9	8
Class B Common Stock
Shareholders' equity
Common stock, value, issued	$ 14	$ 14

Warrant Liability, Noncurrent

No definition available.

Name:	npwr_WarrantLiabilityNoncurrent
Namespace Prefix:	npwr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).