I have a Mighty Bright and I love it! It runs on 3 AAA batteries and seems to work for quite a while between battery changes. I can't give you any solid numbers, because I only use mine during power outages, but I'm still on the first set of batteries (I think they came with it, but I'm not certain) and I've had it since late spring. And a bonus I've discovered - it throws enough light to use as a backup flashlight during a power outage, at least enough to move through the house without breaking toes or bruising shins!