The Sub-Surface Railway of the London Undergroundnetwork is due for a major upgrade in 2015. The upgrade willinclude the procurement of new rolling stock and signallingcontrol system, a significant increase in service frequencies,and a big capital investment in upgrading the powerinfrastructure. Investigation of energy efficient measures,such as optimal train power with use of coasting, higherpower supply voltage, and conductor rail of lower resistance,allowed the system wide costs to be significantly reduced forno loss in upgrade benefits. The optimisation studyundertaken achieved cost savings of amp;amp;#163;25m in capitalexpenditure and amp;amp;#163;80m in whole life costs, as well as a 20%energy and CO2 reduction, for the same customer journeytime performance after the upgrade. The paper describes indetail how this optimisation study was performed.