Is text-only mode a saving or a problem for battery savings?

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http://askubuntu.com – A friend is flying to the US from Europe and asked me a very thought-provoking question, which I am not remotely able to answer with substance so I am asking it here: How to absolutely maximise battery life on an Ubuntu (laptop) install? do not rush to mark this as duplicate, there is an important point here: does -GNOME- help or worsen battery life? Let me provide some context: The only task he needs to perform is: edit text files in Vim. He is unsure whether running GNOME will drain his battery life more or actually save him some battery life given the smarts of GNOME's power manageme (HowTos)