Note 9 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)	Sep. 30, 2025	Sep. 30, 2024
Accrued pension and postretirement medical benefits	$ 556,316	$ 512,778
Regulatory effect of change in federal income tax rate	2,433,559	2,553,086
Cost of gas held in storage	773,167	835,094
Deferred compensation	1,382,130	1,166,850
Impairment of unconsolidated affiliate	13,722,837	14,077,357
Regulatory effect on tax credits	1,277,006	1,437,670
Other	861,076	641,300
Total gross deferred tax assets	21,006,091	21,224,135
Utility property	20,367,400	19,879,747
MVP investment	2,054,156	1,586,837
Interest rate swaps	230,356	530,903
Accrued gas cost	14,339	345,464
Total gross deferred tax liabilities	22,666,251	22,342,951
Net deferred tax asset	617,390	771,746
Net deferred tax liability	$ 2,277,550	$ 1,890,562