What unit does the activity monitor use in the energy tab? The activity monitor of OS X show in the energy tab the energy impact. What unit does this value use? Is it Watts? If so, 327 seems a bit high for my taste. I am running this on the low end 21" late 2013 iMac. Of course, Handbrake will use lots of energy, but I would not think that the iMac can pull as much as 320 Watts.
It's a proprietary unit calculated from other available data about a process, including but not limited to CPU utilisation, both short-term and long-term averages (think load averages).