So... you're not really giving up on mining with $0.15 per kWh? With all the maintenance costs and this price of electricity, I'd recommend you to get your solar energy system completed before increasing the number of your rigs (that solar setup should be your priority IMO). I gave up on mining due to having the power valued at $0.12 per kWh (it didn't really look like being worth it even at that price), and it's interesting to see someone else trying to build up a mini mining farm with an electricity cost more than mine; I sort of appreciate that!
About the wallets, it totally depends upon what YOU are going to plan with your mining revenue. Do you plan on trading them? Or just HODLing them?
There is good stories and there is bad stories. My personal experience has been quite good, started mining eth in 2016 with 13c a kw/h , paid power from my poket. And managed to make good few Zeross with only 6 mining rigs. Its not a luck, i belive harder you work luckier you get...ha ha ha
Not all the times because you wouldnt know on what comes next.Being too optimistic do have its own risk to but on your case it turns out to be some sort of luck that the market did tend to spool up and come to think that not all miners are willing to pay up directly with their own pocket and some are just depending on their mining earnings.
@Raja. for $.12 per kwh its already non profitable how much more on 15.If he decides to proceed in spite of this factor then he do see mining as a hobby. hehe