The study »Beyond replacing diesel trucks: how optimized fleet planning increases electrification and lowers transportation costs« investigates strategies for electrifying heavy-duty truck fleets in the logistics sector without increasing the total cost of ownership (TCO). Using real-world data from over 38,000 shipments in German grocery retail, it compares the conventional 1:1 replacement of diesel trucks with battery electric trucks (BETs) to an optimized transport replanning approach that integrates route and charge planning. Results show that replanning more than doubles the share of electrified transport performance and achieves greater cost savings (up to 8% vs. 3%) while requiring smaller battery sizes. Moreover, it reduces reliance on subsidies and improves utilization. The study concludes that advanced planning software is key to cost-efficient fleet electrification and recommends its broader adoption alongside the development of fleet-level operational capabilities.