We live in Seattle, where it really only gets hot enough for AC maybe a month a year.....mayyybe. We didn't want to spend the $300 on a portable unit so figured we'd compromise and try this out. This is absolutely NOT an AC unit. That being said, it does keep the room very nice and cool just not in the same way. It does leave the room a bit humid, so it helped us to crack some windows open while it was running. It also worked splendidly adding ice to the reservoir. When it runs on high, the water does need to be filled often, we were not able to make it through the night without waking up to see the water indicator light blinking that it was out of water. I'd say on high, it will run 4-5 hours before you need to add water. It's only meant to keep one room cool at at time, so we moved it to each room we were camped out in. I'd say if positioned in a place with adequate air flow, It will keep a about 300 sq ft cooled at one time. So, I'm very happy with this purchase, it got us through a 95 degree weekend.