The developments in electric vehicles (EVs) are driven by the need for cleaner and more efficient road transport, but vehicle charging poses significant challenges to the electric grid and electricity sector planning. These challenges are further amplified in the case of a highly urbanised and densely populated small island state, like Singapore, with limited space and options for electricity sector planning. In response, this study aims to evaluate the impacts of a large-scale EV deployment on the electricity sector from a whole-system perspective with focus on investments in the power sector for EV adoption, assuming minimum deployment of advanced “smart-grid” and “vehicle-to-grid” technologies. Findings suggest that a small-scale deployment of EVs below 20% replacement can be economically manageable. A large-scale of deployment of EVs would inevitably bring a notable impact to the electricity sector regardless the state of advanced technology development. From the perspective of integrated planning, cities, especially those with high vehicle density, should continue to exercise caution with EV deployment. A large-scale deployment should be pursued after a “stress-test” of the power system infrastructure from both the technical and economic perspectives.