Accounting policies - Disaggregated revenue (Details) $ / shares in Units, gal in Millions		12 Months Ended
	Jun. 02, 2023 gal	Dec. 31, 2025 USD ($) $ / shares	Dec. 31, 2024 USD ($) $ / shares	Dec. 31, 2023 USD ($) $ / shares
Accounting policies
Total Revenue		$ 132,073,368	$ 133,966,633	$ 180,211,233
Contracts in progress
Number of days after consumption billings are considered past due		45 days
Income (loss) from operations		$ 18,360,191	18,284,798	37,167,627
Increase in net income		$ 18,336,673	$ 28,237,554	$ 29,585,391
Increase in basic earnings | $ / shares		$ 1.17	$ 1.13	$ 1.95
Increase in diluted earnings | $ / shares		$ 1.16	$ 1.12	$ 1.93
Kalaeloa Desalco
Contracts in progress
Amount of seawater reverse osmosis desalination plant | gal	1.7
Retail revenue
Accounting policies
Total Revenue		$ 33,587,952	$ 31,741,343	$ 30,158,051
Bulk revenue
Accounting policies
Total Revenue		33,481,307	33,673,387	34,595,058
Services revenue
Accounting policies
Total Revenue		46,312,325	50,956,489	97,966,650
Services revenue | Construction revenue
Accounting policies
Total Revenue		13,470,641	18,602,919	77,306,704
Services revenue | Operations and maintenance revenue
Accounting policies
Total Revenue		32,075,046	29,307,405	19,368,365
Services revenue | Design and consulting revenue
Accounting policies
Total Revenue		766,638	3,046,165	1,291,581
Manufacturing revenue
Accounting policies
Total Revenue		18,691,784	17,595,414	17,491,474
Change in accounting method accounted for as change in estimate
Contracts in progress
Income (loss) from operations				2,356,439
Increase in net income				$ 1,750,750
Increase in basic earnings | $ / shares				$ 0.11
Increase in diluted earnings | $ / shares				$ 0.11
Transferred over time | Services revenue
Accounting policies
Total Revenue		13,696,856	18,613,466	$ 77,411,792
Transferred at point in time | Services revenue
Accounting policies
Total Revenue		$ 32,615,469	$ 32,343,023	$ 20,554,858
Minimum
Contracts in progress
Number of days after consumption billings are collected		30 days
Maximum
Contracts in progress
Number of days after consumption billings are collected		45 days