Between 1990 and 2006, the primary energy requirement of the Irish transport sector increased by 166%. Associated greenhouse gas (GHG) emissions have followed a corresponding trajectory, and are responsible-at least in part-for Ireland's probable failure to meet its Kyoto targets. As in most countries, Ireland's transport sector is almost totally reliant on oil-a commodity for which Ireland is totally dependent on imports-and therefore vulnerable to supply and price shocks. Conversely, the efficiency and carbon intensity of the Irish electricity supply system have both improved dramatically over the same period, with significant further improvements projected over the coming decade. This paper analyses the prospects for leveraging these changes by increasing the electrification of the Irish transport sector. Specifically, the potential benefits Of Plug-in hybrid-electric vehicles (PHEV) are assessed. in terms of reducing primary energy requirement (PER) and CO2 emissions. It is shown that, on a per-km basis, PHEV offer the potential for reductions of 50% or more in passenger car PER and CO2 intensity. However, the time required to turn over the existing fleet means that a decade or more will be required to significantly impact PER and emissions of the PC fleet. (C) 2009 Elsevier Ltd. All rights reserved.