Accounting policies - Disaggregated revenue (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Total Revenue	$ 33,591,079	$ 32,479,158	$ 67,306,464	$ 72,168,548
Contracts in progress
Number of days after consumption billings are considered past due			45 days
Income from operations	5,283,764	5,010,790	$ 9,894,527	12,324,784
Increase in net income	$ 5,096,205	$ 15,850,257	$ 9,887,234	$ 22,324,605
Increase in basic earnings	$ 0.33	$ 0.27	$ 0.63	$ 0.71
Increase in diluted earnings	$ 0.32	$ 0.26	$ 0.63	$ 0.7
Retail revenue
Total Revenue	$ 8,638,026	$ 8,181,884	$ 18,049,368	$ 16,806,822
Bulk revenue
Total Revenue	8,274,816	8,447,958	16,686,532	16,790,052
Services revenue
Total Revenue	11,448,202	11,922,469	21,526,470	29,340,080
Manufacturing revenue
Total Revenue	5,230,035	3,926,847	11,044,094	9,231,594
Construction revenue | Services revenue
Total Revenue	2,825,935	4,004,072	5,044,167	13,381,536
Operations and maintenance revenue | Services revenue
Total Revenue	8,255,408	7,068,922	15,980,704	14,168,275
Design and consulting revenue | Services revenue
Total Revenue	366,859	849,475	501,599	1,790,269
Change in accounting method accounted for as change in estimate
Contracts in progress
Income from operations	167,904		445,150
Increase in net income	$ 450,619		$ 450,619
Increase in basic earnings	$ 0.03		$ 0.03
Increase in diluted earnings	$ 0.03		$ 0.03
Transferred over time | Services revenue
Total Revenue	$ 3,104,731	3,988,174	$ 5,284,992	13,385,268
Transferred at point in time | Services revenue
Total Revenue	$ 8,343,472	$ 7,934,295	$ 16,241,478	$ 15,954,812
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