If they were to use only the policy net part of AlphaGo they would need a few milliseconds per move and only one computer to run it, achieving the level of 1p. Also, if DeepMind used specialized Go hardware maybe they could reduce the power usage a lot, but they didn't optimize for that.
For example, it would be interesting to calculate how much power is used in image recognition, man vs machine. The brain uses 20-40W and a cell phone only 5W, and we know cell phones can do image recognition, so, probably the computer uses less than the human given that human reaction time is 200ms and the computer could classify much more than 5 images per second, so it uses less time and consequently less energy per image.