I don't know if this is still relevant to anyone, but this is how I solved it:
In our Company we have tons of Displays that just Display Information, and I was looking, just like the person that asked this question, to reduce the energy my Raspberry Pi's use at night (since no one really needs them at night).
I modified /etc/crontab to kill all tasks (specifically all chromium tasks, as we run the info on an html site) at 8pm. After that my PI used 0.5% of their ram. I also disabled the task bar and made the background black. The PI uses just a little more energy than if he was actually turned off (which you could only do with additional hardware). And it's an easy solution.
(For turning the PC back on, I modified crontab to reboot at 7am and added the website in autostart (/etc/xdg/lxsession/LXDE-pi/autostart)). As a result, all of our PI's use little to no energy overnight.
I hope I was able to help someone that was facing the some problem that we had.
I also want to add that in normal circumstances you dont have to worry about turning your PI off, as it uses little to no energy anyways (especially when you're just displaying something).