Apple Watch draining iPhone 6 battery

Got an Apple Watch Sport on release day - its battery life has been great. iPhone 6 battery is what's suffering. I can't make

it through half the day now without it threatening to completely die. I've hard reset the Apple watch, turned off all non essential notifications and basically am just using the device as a watch. This was definitely not the case before - my phone would easily make it through a 24 hour period with juice to spare.

Nothing seems to help my iPhone battery. Any thoughts?