I Can Save the Earth! by Alison Inches (2008)
Meet Max the Little Monster. He is a cute, furry green monster who is an environmental nightmare. Among other things, he leaves on all the lights, keeps his computer plugged in, blasts the TV, hoards his old toys and uses so much toilet paper it clogs the toilet until finally, his excessive ways cause a power outage. With no TV to watch, computer to play on, video games to play with, Max finds there is a whole big world outside that he can make a difference in the environment.