A 150 m electric wave-piercing catamaran concept from Incat Tasmania is analysed using CFD to explore the hydrodynamic impact of operating speed and hull separation on vessel performance and CO2 emissions reduction. Over the investigated speed range of 0.2 < Fr < 0.4, interference factors are evaluated for four demihull separation ratios (s/L) and two demihull slenderness ratios (L/∇1/3). The implications on total life-cycle CO2 emissions are presented as a function of total vessel resistance, and the significance discussed. A separation ratio of s/L = 0.220 provides the lowest overall resistance, however other configurations provide superior results for specific Froude numbers. The concept of transportation capacity is introduced and used to demonstrate the advantage of slower speeds for the electric powertrain through identification of a critical Froude number Fr = 0.35, above which transportation capacity is reduced as a consequence of the low energy density of Nickel Manganese Cobalt (NMC) batteries. A comparison is also made between the electric and equivalent LNG and diesel powertrains to demonstrate the effect of fuel carbon intensities on standardised vessel CO2 emissions. Through analysis of the transportation capacity and emissions reduction of the electric vessel, a speed of Fr = 0.28 is proposed as a compromise between the two, with further power and emissions reductions achievable near this speed by adopting a narrower hull separation ratio of s/L = 0.151.