Have been reading of this this on a railway forum.

I doubt that diesel locomotives will be cheaper to run than electric locomotives for any significant time.

Red diesel fuel is available for about 80 pence a liter in bulk.

In an efficient diesel generator each liter can produce 5 kwh, or perhaps 4 kwh under less favourable conditions.

That suggests an operating cost for FUEL ALONE of about 16 pence to about 20 pence per kwh for a diesel locomotive. 

Network  rail charge about 12.5 pence a unit for traction current, a clear saving. Some train operators have elected not to pay this flat rate, but instead chose to pay the actual “day ahead” spot price for electricity, plus a network rail markup for distribution costs. That could prove very expensive indeed at times, but I doubt that it would REMAIN more expensive than diesel fuel.

Electric locomotives are cheaper to maintain thereby saving expensive labour, but it is hard to put a direct value on this.

Have been reading of this this on a railway forum.

I doubt that diesel locomotives will be cheaper to run than electric locomotives for any significant time.

Red diesel fuel is available for about 80 pence a liter in bulk.

In an efficient diesel generator each liter can produce 5 kwh, or perhaps 4 kwh under less favourable conditions.

That suggests an operating cost for FUEL ALONE of about 16 pence to about 20 pence per kwh for a diesel locomotive. 

Network  rail charge about 12.5 pence a unit for traction current, a clear saving. Some train operators have elected not to pay this flat rate, but instead chose to pay the actual “day ahead” spot price for electricity, plus a network rail markup for distribution costs. That could prove very expensive indeed at times, but I doubt that it would REMAIN more expensive than diesel fuel.

Electric locomotives are cheaper to maintain thereby saving expensive labour, but it is hard to put a direct value on this.