Interesting topic with running the diesels.
I'm aware of it being done in the Netherlands by the bigger hospitals to keep the peak demand down between 17.00 hrs and 19.00 hrs. without cutting of electrical services.
It is done here in NZ by the railways, that it is sometimes cheaper to run a diesel, dragging 2 "dead" electrics + train behind it than using the Grid supply at certain peak periods during the day.
The charges per ½ hour can be up to 50 cts / kWh at certain TOU periods.
