| 1 | HEPX | Hydro One | added 4/2001; 7/2005 | | NAKINA |
| 2 | HEPX | Ontario Hydro | added 7/1975; 1/1980-7/2000; eliminated 4/2001 | | NAKINA |
| 3 | HEPX | Hydro-Electric Power Commission of Ontario | 1/1952-1/1975; eliminated 7/1975 | | NAKINA |
| 4 | HEPX | Headley Emulsified Products Co. | 7/1930-7/1932 | | NAKINA |
| 5 | HEPX | Hydro-Electric Power Commission of Ontario | 1/52-1/75; eliminated 7/75 | | NRHS |
| 6 | HEPX | Ontario Hydro | added 7/75; 1/80-7/2000; eliminated 4/2001 | | NRHS |
| 7 | HEPX | Hydro One | added 4/2001 | | NRHS |
| 8 | HEPX | *HEADLEY EMULSIFIED PRODUCTS CO. | | | PWRC |
| 9 | HEPX | +ONTARIO HYDRO (HYDRO ONE) | | | PWRC |
| 10 | HEPX | Ontario Hydro (Hydro One) | | | RSRV |
| 11 | HEPX | HYDRO-ELECTRIC POWER COMMISSION OF | | | SCAC4 |
