A novel statistical model for the energy transfer process in Er3+:Yb3+-codoped glasses, e.g. fibers, is presented. The most important advantage of the model is the correct modeling of the energy transfer as a dipole-dipole interaction, as it overcomes the unreasonable but common modeling of the energy transfer as a fixed rate. Exemplary results obtained with the novel model behave reasonable and show good prospects to study optimization strategies of Er3+:Yb3+-codoped fibers. Furthermore, the model can be further developed and expanded in the future, e.g. by including energy migration amongst the individual Yb3+-ions and Er3+-ions.