bro i know that S9 is also in market it will cost arround $2500 in india with 14 TH/s hash rate . and S7 came with 4.73 TH/s & the cost is $550 in india. if i purchase 4 S7 minier then my rig hash rate is arround 18 TH/s , it is profitable? as compare to S9 .
forget about electric cost,
i had place where electric bill is ZERO then. it is profitable or not in 1 years my expense is only internet connection,
If the electric bill is zero go for it!
A reporter recently asked several chinese miners about whether he might stop mining after halving. They replied they wouldn't because they had already invested in hardware and electricity cost is zero so no harm in running.