Note 3 - Segment Information - Segment Information (Details) - USD ($)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Revenue	$ 95,334,212	$ 84,641,232
Operations and maintenance	19,911,410	18,354,736
Taxes other than income taxes	2,933,787	2,694,652
Depreciation and amortization	11,470,641	10,518,094
Operating income (loss)	18,447,501	17,081,760
Equity in earnings	3,234,632	3,851,871
Interest expense	6,543,511	6,504,885
Income before income taxes	17,371,505	15,457,507
Assets	329,839,566	320,699,223
Gross additions to utility property	20,730,140	22,094,406
Gross investment in affiliates	76,385	18,258
Gas Utility [Member]
Revenue	95,231,943	84,533,101
Cost of Product and Service Sold	42,550,954	35,967,987
Operating Segments [Member]
Revenue	95,231,943	84,533,101
Operations and maintenance	19,911,410	18,348,840
Taxes other than income taxes	2,933,787	2,704,540
Income before income taxes	17,289,155	15,369,499
Assets	313,250,313	301,833,350
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Revenue	102,269	108,131
Operating income (loss)	19,919	20,011
Income before income taxes	82,350	88,008
Assets	16,589,253	18,865,873
Gas Utility [Member]
Revenue	95,231,943	84,533,101
Depreciation and amortization	11,470,641	10,518,094
Operating income (loss)	18,549,566	17,130,480
Equity in earnings	0	0
Interest expense	3,706,152	3,700,674
Income before income taxes	17,072,877	14,459,009
Assets	291,571,159	280,508,989
Gross additions to utility property	20,730,140	22,094,406
Gross investment in affiliates	0	0
Gas Utility [Member] | Gas Utility [Member]
Cost of Product and Service Sold	42,550,954	35,967,987
Gas Utility [Member] | Operating Segments [Member]
Revenue	95,231,943	84,533,101
Operations and maintenance	19,729,415	18,215,354
Taxes other than income taxes	2,931,367	2,701,186
Income before income taxes	17,072,877	14,459,009
Assets	291,571,159	280,508,989
Gas Utility [Member] | Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Revenue	0	0
Operating income (loss)	0	0
Income before income taxes	0	0
Assets	0	0
Investment in Affiliates [Member]
Revenue	0	0
Depreciation and amortization	0	0
Operating income (loss)	(184,415)	(136,840)
Equity in earnings	3,234,632	3,851,871
Interest expense	2,837,359	2,804,211
Income before income taxes	216,278	910,490
Assets	21,679,154	21,324,361
Gross additions to utility property	0	0
Gross investment in affiliates	76,385	18,258
Investment in Affiliates [Member] | Gas Utility [Member]
Cost of Product and Service Sold	0	0
Investment in Affiliates [Member] | Operating Segments [Member]
Revenue	0	0
Operations and maintenance	181,995	133,486
Taxes other than income taxes	2,420	3,354
Income before income taxes	216,278	910,490
Assets	21,679,154	21,324,361
Investment in Affiliates [Member] | Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Revenue	0	0
Operating income (loss)	0	0
Income before income taxes	0	0
Assets	$ 0	$ 0