The importance of the cathode assembly thermal-electrical and thermal-mechanical performance cannot be overstated when designing an aluminum reduction cell. However, it is extremely difficult to measure in-service cathode assembly performance or to infer in-service behaviour from any measurements of cathode assemblies at room temperature. A complete thermo-electrical and thermo-mechanical modelling approach has been developed to conduct sequentially coupled simulation of the cathode assembly lifecycle performance. The modelling starts with the cathode rodding process which allows the air gap between the cast iron and carbon to be predicted. The results are built into the subsequent thermo-electrical and thermo-mechanical models of the in cell operation. The cathode voltage drop is then estimated by coupling the predicted contact pressure and temperature with the electrical contact resistance. The model predicted air gaps as well as cathode voltage drop savings due to design changes have been validated by carefully designed experimental measurements for various cathode assembly designs.