I have the city of Kirkminster (3MW demand) which has within its city limits a fishmonger (3MW demand) and a coal-fired power station (69MW output). I wanted to supply power to the city so I built an upstream substation next to the power station, ran a power line out and back into the city, and placed a downstream substation within the city to power it. What I expected was to see was a 6MW demand for the city and the fishmonger, but the demand is actually 75MW. It would appear that it is incorrectly counting the power station's generation as additional demand for the city.
Here is a save of my map right before attempting to add any substations: http://simutrans-germany.com/files/upload/Anthony9a.zip
Please let me know if you have any questions, and thanks!
Thank you very much for your report. I will look into this when I get some time.
Thank you again!
I have now found and fixed this problem on the 11.x branch - apologies that I forgot to get around to this in time for the 11.14 release.