At this very moment, you may be paying too much on your utility account and have no idea.
Municipal and Eskom electrical billing errors aren't always clear, you have to understand that all billing is derived from technical information.
A smart meter can be installed incorrectly, the meter can be programmed incorrectly and lastly, the information acquisition and transfer can be managed incorrectly.
Once the technical information is passed through to billing, the applicable tariff is applied. In many cases, while the application of the tariff may be correct, the engineering values may not. One can at least audit the tariff rates and structures on the utility account but one can't validate the accuracy of the source engineering values. All these issues can result in "hidden" errors on your account and you will have no idea that you are being billed incorrectly.
The only way to ensure that the engineering values on your utility account are correct is to install a check meter that is in line with the Municipal or Eskom meter and compare your check meter engineering values to that of your Suppliers.
Check out www.utilman.com for automated utility audits.