Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Current assets
Cash and cash equivalents	$ 117,933	$ 199,430
Investments in securities, available-for-sale	190,437	138,462
Interest receivable	870	1,376
Prepaid expenses and other current assets	3,669	4,496
Total current assets	312,909	343,764
Long-term assets
Restricted cash	1,206	2,427
Investments in securities, available-for-sale	0	38,242
Intangible assets, net	402	181,572
Property, plant, and equipment, net	23,392	32,758
Operating lease right-of-use assets	269	551
Other long-term assets	147	387
Total assets	338,325	599,701
Current liabilities
Accounts payable	124	1,437
Accrued liabilities	4,864	7,565
Due to related parties	6,976	37,262
Operating lease liabilities, current	1,091	1,074
Finance lease liabilities, current	33	127
Asset retirement obligation, current	4,490	0
Total current liabilities	17,578	47,465
Warrant liability	5,770	10,850
Non-current operating lease liabilities	2,180	2,584
Asset retirement obligation	0	3,597
Total liabilities	25,528	64,496
Commitments and contingencies (Note 14)
Mezzanine shareholders' equity
Redeemable non-controlling interests in subsidiary	229,270	331,301
Shareholders' equity
Preferred Stock, $.0001 par value; 1,000 shares authorized; no shares issued or outstanding as of June 30, 2026 and December 31, 2025	0	0
Additional paid-in capital	868,368	898,425
Accumulated other comprehensive (loss) income	(44)	129
Accumulated deficit	(784,820)	(694,672)
Total shareholders' equity	83,527	203,904
Total liabilities, mezzanine shareholders' equity, and shareholders' equity	338,325	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).