The carbon intensity of the UK electricity grid is currently experiencing a fast reduction as a result of increasing the share of power generation from renewable sources, particularly wind. The UK energy policy towards achieving zero carbon emissions by 2050 requires both the building and transport sectors to be decarbonised. This, however, presents a huge technical and economical challenge in that all heat generation in buildings needs to be supplied from electrically-driven heat pumps and fossil-fuelled private vehicles be replaced by electric vehicles (EVs) which are affordable to consumers. Achieving such an ambitious goal will require the power generation capacity to more than double which in turn exacerbates the issue of intermittency of renewables and low inertia in the grid system. This paper attempts to analyse the current UK grid system critically and addresses the question of what will happen to the UK’s electricity grid under large-scale RES integration and high EV penetration. With the increasing number of EVs connected to the grid for charging, management of plug-in EVs becomes critical to maximise the use of renewables, particularly at times of excess generation.