Electric Road System (ERS) is a technology concept that has the potential to heavily reduce fossil fuel dependency. ERS is defined by dynamic power transfer from the road to the vehicle while the vehicle is in motion and could be achieved through different power transfer technologies from the road to the vehicle such as rail, overhead-line, and wireless solutions. The investment cost to implement ERS will be high and decision makers will require knowledge about how mature different solutions are compared to the conventional and alternative technologies. However, while there are numerous ERS development and demonstration projects globally, it is unclear which technological solution that is best suited for large scale implementation. Drawing on the method associated with Technology Readiness Levels (TRLs), this article evaluates the maturity level of the different ERS technologies and focuses on the power transfer technology subsystem. Thereby it contributes to discourse on sustainable transportation and the development of ERS.