It is recommend that you use the DeltaV Controller Load Estimator Tool to determine the number of DeltaV controllers needed for your project. This utility estimates controller CPU utilization and memory usage based on the Modules, Sequential Function Charts (SFC), Phase Logic Modules (PLM), and Unit Modules assigned to a controller. This is useful in the initial phase of the project when the number of I/O channels, loops, PLMs, and SFCs is known. The accuracy of the estimate is expected to be 20% of the actual load. You can achieve greater accuracy by entering your own custom modules that more closely match your configuration. Typically, CPU loading is expected to be 20% more for redundant controllers than for simplex controllers. However, in practice, CPU loading of redundant controllers could be higher depending upon the system configuration and process operation.