Hi all,
I'd like to implement the feature of "energy rate" in the actual Battery Monitor Plasmoid of KDE, because in new releases of KDE kpowersave doesn't woth anymore

Any advises about this?
I know that I've to use upower interface but...I don't know from to start

I would suggest asking on the kde-hardware-devel@kde.org mailing list about this. The developers there should know if the change is appropriate and where to make those changes.