A water heating apparatus includes a water tank having a plurality of sidewalls, a main heating member mounted inside and across the water tank, and at least one secondary heating or partition member extending between the main heating member and the sidewalls to form at least one water compartment with a water path. At least one tertiary heating member is provided on the inner surface of the water tank. The partition member can be spiral in shape. Each heating member has at least a multi-layer conductive coating of nano-thickness deposited thereon, and electrodes coupled to the multi-layer conductive coating. The multi-layer conductive coating comprises a structure and composition which stabilize performance of the heating member at high temperature.