XPS 15 9500, battery drain issue

Hi, 

I've just received my Dell XPS 15 9500 (i7 + FHD) laptop. After updating all my Dell and windows drivers I realised I was only getting approximately 3hrs of battery life on  'best battery saver' mode and 40% brightness whilst surfing the web. 

I've since reinstalled windows and reinstalled all the updates. Additionally, I've also limited all startup applications to the absolute minimum and opted for integrated graphics wherever possible within the NVIDIA control panel. However, still experiencing ~3hrs of battery life well short of the purported 20+ hrs

I can't seem to find a solution on the internet, just wondering if anyone else was experiencing the same issues? and any ideas how to solve this?

I also downloaded battery bar and it suggests I am discharging at 20-35W which I understand is very high.