In the course of this doctoral thesis multirate and co-simulation methods will be examined. Research topics on the one hand include numerical aspects of different methods including dedicated special cases and on the other hand display defined problems, yet without sufficient solution approaches to be detected and investigated later on. Additionally, preceding analysis and subsequent implementing tests are used to ascertain sensible cases for the use of multirate or co-simulation in industrial cases of application. These investigations can be used to determine the true benefit of co-simulation approaches for the increase of energy efficiency in production facilities. Further, the results of this project allow the definition of numerical stability regions and hence warranty for accuracy requirements when coupling simulations for the calculation of complex models of large-scale companies.