Ok, sufficiently baited to do an actual response 
In addition to fully agreeing to brinebold (e.g. stress on GPU), even the electricity cost is a relative thing.
Personal example:
I am living in a house which (typically french I guess) has electrical heating only. Most of the rooms are heated by one electrical radiator per room, the total electricity the heating eats up in the winter months is about 3kW total.
I could replace the radiators in a few rooms by mining rigs at 0 electricity cost. Any W they use ends up as heating in the end, saving me the same W in electrical heating.
So even if GPU mining drops to the point (very location -> electricity price dependent) where it technically doesnt look profitable power cost wise, 5-6 months of the year I could mine for no running costs at all.
Whether one thinks its worthwhile to buy rigs or upgrade machines specifically for mining is a different question, which everyone knows best himself i guess.
P.S.: I wrote a lot of "could", the above actually was my plan for last winter, as I have a few slightly outdated PCs standing around (that can still fit 5790s), but then was too busy with other stuff to actually set it up
In addition to fully agreeing to brinebold (e.g. stress on GPU), even the electricity cost is a relative thing.
Personal example:
I am living in a house which (typically french I guess) has electrical heating only. Most of the rooms are heated by one electrical radiator per room, the total electricity the heating eats up in the winter months is about 3kW total.
I could replace the radiators in a few rooms by mining rigs at 0 electricity cost. Any W they use ends up as heating in the end, saving me the same W in electrical heating.
So even if GPU mining drops to the point (very location -> electricity price dependent) where it technically doesnt look profitable power cost wise, 5-6 months of the year I could mine for no running costs at all.
Whether one thinks its worthwhile to buy rigs or upgrade machines specifically for mining is a different question, which everyone knows best himself i guess
.P.S.: I wrote a lot of "could", the above actually was my plan for last winter, as I have a few slightly outdated PCs standing around (that can still fit 5790s), but then was too busy with other stuff to actually set it up