A multiscale modeling approach was utilized to predict thickness reduction in steel plate heat exchangers (PHEs) utilized in combi boilers. The roles of texture and microstructure were successfully accounted for by properly coupling crystal plasticity and finite element analysis (FEA). In particular, crystal plasticity was employed to determine the proper multiaxial hardening rule to describe the material flow during the forming of PHEs, which was then implemented into the finite element (FE) metal-forming simulations. The current findings show that reliable thickness distribution predictions can be made with appropriate coupling of crystal plasticity and FEA in metal forming. Furthermore, the multiscale modeling approach presented herein constitutes an important guideline for the design of new PHEs with improved thermomechanical performance and reduced manufacturing costs.