Even if it's 5W, it's going to charge during the whole time you're in the charger's vicinity aka in the room the charger is placed in. 5W over a span of 3 hours is the same as 15W over a span of 1 hour. And smartphone batteries aren't usually big enough to require more than 5W over 3 hours to go from 0% to 100%. Efficiency and potential human/animal safety and/or device health concerns aside, this is pretty interesting.