| Group | Class | Sub - Class | Description | 
                    
                        | 401 | 4010 |  | Production , collection and distribution of electricity | 
                    
                        |  |  | 40101 | Generation and transmission of electricity: hydro-electric power plants | 
                    
                        |  |  | 40102 | Generation and transmission of electricity: coal based thermal power plant | 
                    
                        |  |  | 40103 | Generation and transmission of electricity: oil-based thermal power plants | 
                    
                        |  |  | 40104 | Generation and transmission of electricity: atomic reactor power plants | 
                    
                        |  |  | 40105 | Generation and transmission of electricity: other power plants using conventional fuels (e.g. gas based) | 
                    
                        |  |  | 40106 | Generation of solar energy | 
                    
                        |  |  | 40107 | Generation and distribution of bio-gas energy | 
                    
                        |  |  | 40108 | Generation of electricity from other non-conventional sources. | 
                    
                        |  |  | 40109 | Collection and distribution of electric energy to households, industrial, commercial and other users n.e.c. | 
                    
                        | 402 | 4020 | 40200 | Manufacture of gas; distribution of gaseous fuels through mains | 
                    
                        | 403 | 4030 | 40300 | Steam and hot water supply |