Limiting the amount of power used in my project

I am trying to set up a switch/pushbutton to be used with my Arduino project that will reduce the amount of power used during the time that the switch/pushbutton is pressed. I currently used an L293D H-Bridge and wondering.. Can I use commands to lower the amount of power that the H Bridge is using when the switch/pushbutton is pressed/held down? I already have it so my LEDs are set to LOW, all thats left is my ATMEGA328 and the L293D H-Bridge, both of which are on breadboards to cut down on power wasted on other functions that I've heard Arduino Uno sucks up.