For shits amd giggles, I put a couple of industrial 10W fans in my PC once. That probably still made more noise than this. It also created so much overpressure that I could feel air escaping the tower from every little hole or crack. You could hold a piece of paper to the side of the pc, and see it moving because of the air escaping between the side panel and the main hull.
But if these are normal fans (max maybe 1,5W), then the amount of power drawn will be the same as a couple of hardrives.