For my use case, shutting off/turning on a water flow of to my heading system I can buy two different type of valves, mototed ball valves and solenoid valves. Most of the time the valve (either option) is not doing anything but is changed (open -> closed / closed -> open) maybe 4 times a day.

My question is about the (idle) energy consumption while there is not action happening. Does a solenoid not work by constantly iducing a magnetic field, hence consuming energy? 
Would a servo motored ball valve be better then, or is either case using energy in idle state (at least either for open or for closed?)