This study presents a theoretical analysis to quantify power losses generated by an oil-jet lubricated deep groove ball bearing. Loaded rolling elements (RE) have been thoroughly studied in the past for the Elasto Hydrodynamic Lubricated (EHL) regime, while a wellknown problem concerning rolling element bearing (REB) power losses is the estimation of dissipation sources in the case of limited or no applied load. The model presented in this paper aims to solve this problem by describing the physics involved on the unloaded zone. Unloaded RE are considered in an Iso Viscous Rigid (IVR) regime. The model is compared with global power loss models such as Harris-Palmgren or SKF models. This work shows that unloaded RE can generate around 40% of the losses when the applied radial load is about 5% of the static capacity.