Reducing emissions with battery-electric tugboats and why the ‘where’ matters. With goals of decarbonization and sustainability, the marine industry is investing in its future fleet. As naval architects, Robert Allan Ltd. supports shipyards, owners, and operators in these endeavours. By deploying RAptures, an in-house modelling software used to evaluate the trade-offs of various propulsive powering configurations, the most efficient, economical, and environmentally-sound solutions are identified for clients on a case-by-case basis. RAptures’s capabilities have been upgraded to more accurately evaluate the environmental impacts of conventional and alternative powering systems by employing a lifecycle analysis approach. The updated methodology estimates the total GHG and air pollutant emissions from both onboard fuel consumption and the often-ignored upstream sources during fuel or electricity production and distribution. As the focus of this presentation, RAptures is used to evaluate the emissions reduction potential of the ElectRA 2300-SX battery-electric tug relative to a diesel-fueled equivalent. The first two vessels of this series are set to begin operations in Vancouver Harbour next year and are now under construction. For operations in the Port of Vancouver, which is supplied by renewable hydroelectric power, the ElectRA 2300-SX is anticipated to offer 99-percent lifecycle GHG emissions savings and virtually eliminate air pollutant emissions when running solely on battery power. However, by changing the vessel’s home port, the results tell a different story; for operations in the Port of Melbourne, Australia or the Port of Tianjin, China, the ElectRA 2300-SX would have a 33-percent larger carbon footprint than a diesel-fueled tugboat. By expanding the scope of RAptures to consider emissions from all stages of the energy cycle, the true environmental impact of alternative powering is revealed. It is shown to be highly dependent on operation location and deserves serious consideration when designing the vessels of the future.