Upgrading efficient reactions of microwave-assisted chemistry to the level of industrial technology is slowed down by difficulties in development of large-scale productive reactors. This project demonstrates that microwave reactors can be designed with the help of computer optimization. We outline a CAD approach based on the application of an ANN optimization to a microwave reactor. This technique is used to determine the geometry of a system considered as an enlargement of a small reactor. Functionality and practicality of the technique is demonstrated by its application to MiniFlow 200SS batch reactor from SAIREM SAS. Viability of the approach is illustrated by examples of three-parameter optimization of larger systems guaranteeing, for a given reactant, at least 90% energy efficiency.