The standard splashback height in Australia for an electric or gas cooktop is typically 600mm electric and 650mm for gas off the benchtop. This is considered to be the optimal height to protect the walls behind the cooktop from spills and splatters while cooking. However, it is worth noting that this height may vary depending on the height of the cooktop and the individual preferences of the homeowner. It is important to ensure that the splashback is installed at a height that is comfortable for the user, and that it provides adequate protection from splatters and spills. Always refer to the cooktop and rangehood installation instructions, as the manufacturer may have specific requirements for the installation of the splashback that may differ from the standard height. The installation instruction will have specific guidelines and recommendation on the height of the splashback and other details, it is crucial to follow them to ensure the safety and optimal performance of the appliances.