Access to an inexpensive and reliable supply of energy is critical for the success of modern civilisation. Since the beginning of the Industrial Revolution in the mid 18th century, fossil fuels have enabled great advances across many aspects of society, which have increased the standard of living for many. Unfortunately, dwindling supplies and greenhouse gas emissions resulting from their use means that the continued utilisation of these fuels - particularly for electricity generation and transportation - is simply not sustainable. Present-day electricity systems are built around the premise that generation is flexible and controllable, while load - generally speaking - is not. This leads to dispatch models where generation is scheduled to meet load, plus some additional capacity to accommodate forecast errors and potential equipment failure. Many renewable generation technologies, such as wind and solar photovoltaics, are non-dispatchable and cannot be scheduled to produce electricity on-demand. Successfully utilising these energy sources therefore requires flexibility in other parts of the system. Electric Vehicles (EVs) produce no tailpipe emissions, and can be charged at any location with an electricity supply; at home, work, supermarket, or dedicated charging facilities. Because driving times tend to coincide with existing peak electricity demand, EV charging will occur at times of already high electricity demand if not controlled. Fortunately, there is substantial flexibility over the timing of charging, which can be exploited to minimise adverse impacts on electricity grids. Additional benefits are realised when energy is allowed to flow from the vehicle's battery back into the electricity grid; a concept known as vehicle-to-grid (V2G). Through the development of a simulation based on future energy scenarios in New Zealand, the research presented in this thesis evaluates the extent to which the flexibility of EV charging may be exploited to support high levels of non-dispatchable renewable electricity generation. Several EV charging strategies are introduced and evaluated across a range of metrics with wind penetration levels ranging between 10% and 50% on an annual energy basis. With a V2G-enabled fleet consisting of one million vehicles (25% of New Zealand's projected light vehicle fleet size in 2030), it is found that EV charging is sufficiently flexible to the extent that electricity generation does not need to follow daily variations in load. The EV fleet is capable of meeting the power and ramping requirements of the electricity grid, in addition to its own transportation needs, so long as sufficient energy is generated within a few days of its consumption. Such flexibility is expected to greatly assist the future expansion of non-dispatchable renewable electricity generation in New Zealand.