During seven Friday evening “Illini Lights Out” events in the 2016-17 academic year, teams of student volunteers switched off more than 11,000 fixtures and closed windows in campus buildings around the Main Quad at the University of Illinois at Urbana-Champaign. One bulb at a time, this small action taken by more than 200 students saved campus about $3,400 in energy costs — not to mention lengthened the lifespan of several thousand lightbulbs.