A dishwasher and associated control method are provided wherein a water supply manifold supplies a wash chamber with wash liquid. The supply manifold includes a hot water inlet from an external hot water source and a separate cold water inlet, and is configured to be selectively actuated between the hot water inlet or cold water inlet. A controller is in communication with the supply manifold and is configured to act on a signal that is indicative of an actual or pre-defined high electricity demand period on a power supply to the hot water source. The controller is configured to generate an output control signal to the supply manifold to cause the manifold to direct substantially only cold water from the outlet to the wash chamber during the high electricity demand period.