It undoubtedly does, but I haven't noticed my 920's battery life dropping through the floor or shooting up of its on or off regardless of the warning, probably was judged negligible in its drain for the most part.
What device do you have? I've never noticed issues with battery life and double tap to wake on my 920, and I've used that feature as long as it's been available.
It was noticeable I think but very minor. I have multiple email accounts with push notifications and other stuff that eats far more battery life so I leave it on on mine. NFC too for that matter.