The operating range of turbopumps is being extended to higher pressures as a consequence of many demanding applications. Varian VPT has specialized in the design of Gaede stages for extending the operating pressure of the pump. The present work is an extension of the activity made in the last five years in the direction of a good understanding of the behavior of the Gaede stage in viscous flow conditions. Starting from the analysis of the pressure distribution into a single stage, already presented in a previous paper, a transitional power consumption model is derived. The model allows to predict the power consumption of a single Gaede stage as a function of the pumping channel dimensions and clearances, the rotational speed, the nature of the gas pumped, and the operating pressure. The model is based on three main assumptions: (1) the pressure distribution along the channel satisfies a diffusion viscous model at zero net gas flow, (2) the gas flow boundary layer across channel is derived from a simple viscous model, and (3) the gas viscosity obeys a transition expression valid for the pumping channel geometry. Results are compared with the experimental data provided by different single Gaede stages, with different dimensions, at different speed and operating pressure. The behavior of the model with different pump stage clearances is analyzed and results are compared with the experimental evidence. A useful utilization of the model is in the optimization of the design of multistage Gaede pumps.