I asked KNC to confirm that the 1.6 J/GH is at the wall but they did not. Given that the at the wall efficiency will depend on the user supplied power supply efficiency I think the most probable scenario is that the 1.6 J/GH represents the entire system DC wattage. At the wall would be ~10% lower for the average 80Plus Gold PSU. Unless KNC states in clear terms the at the wall/plug efficiency we won't know until some units get to users.
It obviously a mathematically modeled efficiency as there have never been any KNCminer chips to actually measure, it might be right out! They should have the chips this week so it wont be long until we know the real figures, no point speculating. Their design needs several power hungry fans and big expensive heat sinks, which means the chips were planned on being driven hard. If they ever sold the chips separately I would under clock them until they only needed a basic case fan.
i dont think you understand fans and heatsinks....