Anyone remember how when Maxwell was out, Nvidia fans constantly bragged about power efficiency, especially with respect to AMD's Hawaii GPUs.... Now, somehow magically, efficiency is never even uttered by them and even argued that it's not important at all in some cases.
AMD has already claimed that the efficiency of the new 7000 series is increased over the 6000 series, which is a good step, but with Nvidia cranking up the power consumption, it's very possible AMD may have to do the same to ensure a respectable level of competition, which is a shame. It's analogous to how in sports, if a sizable amount of the players are using performance enhancing drugs, an athlete who isn't using them and normally wouldn't, is highly incentivized to start using them. With the state of the world being what it is, we should be striving to use less power, but sadly, it's a well documented phenomenon that technological gains in efficiency never coincide with an overall decrease in power consumption, it's called the "Rebound Effect".