Install a solar water heater
This can save the most electricity of all. It typically saves about two thirds of water heating cost, but this varies and it should be installed with a timer for the best possible saving. With rising electricity tariffs, along with an Eskom rebate, the payback period is now no more than 5 years. Install a heat pump as an alternative, if a solar water heater is not possible. Heat pumps can achieve similar savings but they are a new technology for homes, so they are not well tested yet and may require more maintenance than a solar water heater.