One reason for Caltrain electrifying was to control "fuel" cost. Looks like it worked. They're regenerating and giving back to the grid over 20% of the power used to run the system. And so far their power cost, for running more trains than they did with diesel, is lower than what the diesels used to cost them.
So the fuel cost is lower. Early studies predicted that, and Caltrain needed it to stay in business.
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