| Year | Changing PHCN Price =N=/kWh | Corresponding Unit Cost =N=/cu.m |
| 1992 | 1.50 | 59.12 |
| 1993 | 3.00 | 62.89 |
| 1998 | 4.50 | 66.65 |
| 1999 | 6.00 | 70.43 |
| 2000 | 7.50 | 74.18 |
| 2001 | 7.50 | 74.18 |
| 2005 | 12.00 | 85.48 |