A method for operating a subplant included in a central plant includes obtaining instruction-based equipment models associated with devices included in the subplant and comprises operating points that define an operation of the devices, generating, for each instruction-based equipment models, a geometric equipment model using the operating points from a particular instruction-based equipment model, the geometric equipment model defining at least one operating domain associated with the particular device, merging geometric equipment models to form a geometric subplant model, the geometric subplant model defining an operation of the subplant comprising devices associated with the geometric equipment models, receiving a desired operating point comprising a load value, determining, relative to the desired operating point, a nearest operating point on the geometric subplant model, setting the nearest operating point on the geometric subplant model as an actual operating point, and operating the subplant at the actual operating point for the subplant.