Powering trains by electricity is 95% efficient compared to the 30-35% efficiency of conventional diesel electrics.
… Thus an electrified locomotive can provide the same service for 44.7% of the energy costs. This is a conservative estimate since railroads would buy in bulk at heavily discounted rates.
Around the world electric locomotives are cheaper to buy and operate.
PG 19-20+ in Solutionary Rail’s Book (Chapter 2)