What does Bluetooth do on iPads?

Connect to Bluetooth device such as keyboards, headsets, car audio systems, etc.

http://support.apple.com/kb/HT3647

Regards.

It will obviously use more but i never turn bluetooth off on mine and its not that great impact. I would say from a full charge with standard use with bluetooth it goes down to about 70% comapared to maybe around 85% with bluetooth off.

Hope this helps