Anyway as I don't need it to be running 24/7 but rather there are couple hours in night, when there is definitely no need to have it up.
Electronic timer switchAs I had a chance to buy electronic timer switch at "Flohmarkt" (in Riem seems to be one of the biggest ones), as it was a good deal I bought 3, where 2 seem to work (still it was worth it). After some googling I've found quite detailed manual (for I guess the British version).
Final setupI ended up with following:
- electronic timer switch has been programmed in the way it turns off at 01:00am and goes back on at some time in the morning (depending on weekday or weekend) and
- cron job has been setup to switch the Raspberry Pi 5 minutes before hard unplug (in my setup are 5 mins enough):
# m h dom mon dow command 55 0 * * * /sbin/shutdown -h now