I want to rip DVDs and play them on my netbook on flights. Are there specific video codecs/file formats that use less processing power during playback?
CPU will draw a lot more power than hard-drive activity, so raw uncompressed (or lowest-compression possible) would consume less power.
High-resolution/HD media would also be one to avoid or down-convert.
I would assume the difference would be marginal though.
Hardware acceleration for the H.264 codec is widely available in most modern devices. RAW uncompressed video theoretically uses the least processing power, but it is an impractical choice for the size/quality ratio. (A minute of video alone will occupy over a GB - just how many movies will you be able to store like that?)
My recommendation would be to use the MP4 container with the H.264 video codec (and AAC audio) for maximum possibility of hardware acceleration.