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Note 14 - Commitments and Contingencies (Details Textual)
 12 Months Ended
Sep. 30, 2025
USD ($)
BTU
$ / item
Sep. 30, 2024
USD ($)
Asset Management Contract Term (Year) 3 years  
Energy Purchase Obligation Due In Next Twelve Months (British Thermal Unit) | BTU 2,071,061  
Energy Purchase Obligation Due In Third Year (British Thermal Unit) | BTU 295,721  
Purchase Commitment Minimum Volume Required $ 1,360,000  
Franchise Agreement Term (Year)   20 years
Franchise Fee Annual Increase   3.00%
Franchise Fee Total Cost Through End of Agreement $ 1,690,215  
Energy Purchase Obligation Due In Second Year (British Thermal Unit) | BTU 2,071,061  
Natural Gas Pipeline And Storage Capacity [Member]    
Cost of Product and Service Sold $ 40,843,000 $ 30,880,000
Natural Gas Pipeline And Storage Capacity [Member] | Asset Management Arrangement [Member]    
Cost of Product and Service Sold $ 4,180,000 $ 1,048,000
Minimum [Member]    
Purchase Commitment Purchase Price Per Energy Volume (in USD per Per Share) | $ / item 2.92  
Maximum [Member]    
Purchase Commitment Purchase Price Per Energy Volume (in USD per Per Share) | $ / item 4.13