Thanks for an idea. Maybe in the future, I'll use it. But I've figured out the probably simpliest solution.
Basically, at each plot, there'll be a small storage of energy, which I'll have to check each week and via OC measure consumed energy. After measure, I'll charge storage, which owner of the plot will be using for another week...
It's not a central controlled system, but that could be easily done. The most impotrtant thing is, that this is simple. And as once one smart man said; "There is beauty in simplicity."
Anyway, thanks for the help. Really appreciate it.