€0.27 per kWh means an S3 will cost you roughly €2.20 per day to run. Currently, that S3 expects to make €0.97 a day.
For an S5 you'll do a little better, but still not going to make anything... €3.82 to run a day, expects to make €2.91 a day.
Might want to hold off on taking it to the next level
Not only would she be upset, for once she would have a good reason to be upset
I actually wasn't planning on taking it to the next level anyway, i was aware of the fact that the more hashing power i burn in my home, the more money it'll cost me. Energy prices in my country are insane...
I'm just going to use my (future) U2's to mine some BTC and to experiment. I'm aware of the fact that running a server (i've got an old HP Proliant gathering dust) with those 2 usbsticks will consume a lot more power that can ever be made with the BTC it'll mine... But i don't really care
Rather than fire up an old HP server, you can easily plug those sticks into an rPi, or even whatever laptop you're currently using. I've got 5 of them in a powered USB hub, and that hub is plugged into my rPi. The rPi has cgminer 4.9.1 compiled from source running. I point them to -ck's solo pool because you never know .
The cost to run it is virtually negligible... the U2s draw about 12.5W total and the rPi about 2.5W. 15W total consumption costs me about $0.04 a day. With your insanely high electricity costs, that same setup would cost you about €0.10 a day. Since you're only talking about 2 U2s, that would be a total power draw of 7.5W and about €0.05 a day. Pretty sure you could slip that one by the wife without notice .
Of course, solo mining with only 2 U2s, you've got about a 1 in 617589 chance a day of finding a block at current difficulty levels... but at the cost of playing, it's worth it.