Households are taking in supply at low tension (LT). LT tariffs are typically higher than high tension (6.6 kV and above) due to losses, etc. Also, the tariff being paid by households is a "bundled" one in that it actually contains several components, such as use-of-systems, etc.
You can see the different tariff structures at Singapore Power's website. These are currently regulated tariffs. However, some major HT consumers are already purchasing from private retailers at much better rates.