Best setting for battery saving

Hi,
I would like to re-encode my video to save the battery of my iPhone 6 (not iPhone 6 Plus) when the movie is played
Which are the best settings ? (size, codec, framerate, etc )?
Thank you for your help.

Your best bet will be to ensure the video is encoded in h.264. Everything else (audio, resolution, etc…) won’t make much of a difference.