Does connecting an external display use more battery power than normal use? I will often connect my 13" 2014 MBA to my 1080p TV via HDMI and watch 2 hours of Hulu while the laptop is on battery power. I keep the MBA display on during this time. After 2 hours I always have 50% battery life left, give or take 5%. I thought that I was supposed to get 12 hours?