This is something I know.
I am installing turnkey PV solution & small mining farm
.
Background: here (Italy) the Kw/h cost 0.23 to most of the people.
If you install PV system you got a 10 year tax deduction for 50 % of the value.
Cost of a 3 KW peak solution without the battery 5K €.
Cost of a 3 Kw peak solution with the lithium battery for 5KWh, around 10K( that depends on how many hour/day you need)battery cost coming down 20% year.
You can sell Energy back to the grid at around 0.06 €
A 3KW(peak) system produce South oriented around 3800 kwh/ year.
Problem is when it produce the energy:
1 mining rig ATW absorb 1Kwh = 24 Kwh a day=8670 Kwh/year ,
So it seem that with 7/8 Kw peak installed you can cover your mining rigs at around 100%.
You will need grid connection aniway because if it rain for a day or so.. and if its winter..
So, for 1 rig you need a battery system that can handle 12hour average and as mininum a 12 Kwh battery. Cost for a system ? lets say 26K euro.
Your normal cost for running 1 rig from the grid is 2000 €/year, and just mining Ethereum you will earn, at wtm calculation 2250€.
So, you are looking for a 13 year ROI ( escluding the mining system).
Tax deduction included is 7 year ROI( you will still have to receive some energy from the grid due to weather)
From the mining perspective I normally prepare a system that run CN7 during the night and Neoscrypt,Claymore Dual Keccak during the day because of the difference in power absorption.( you can optimize the timing it start better as some inverter give you by wifi realtime production info but its not worth for just 1 rig).
Who does it ?
A family with an house, with a regular job that can deduct the taxes.
A small company owner its the normal candidate. Cost of equipment can be deducted from the company, but earning in crypto ( at least for now) are not subject to the taxation system. And are not even supposed to be reported if less than 50 BTC.
Some people not happy with the 2% you can earn from the eurobond
and
ME & my friend
)
Kindly note, I haven't take my coffee yet, so calculation can be not so accurate.
If you need anything, just ask,its free, and I still have to thank you a lot of people for what I learned in this forum