Yes I am in the USA.
Residential electric in the USA is supplied by a split phase 120v system. It's a 4 wire system with 2 hots, 1 neutral, and 1 ground. The ground and the neutral are NOT the same thing. The neutral carries live current and will kill you if you touch it. The ground is generally safe unless your house happens to get hit by lightning when you touch it.
When electric is supplied to your outlets they run 3 wires, 1 hot, a neutral, and a ground. This provides 120v -> neutral, and grounding for safety. Because the system is split phase, when one hot is +120v the other hot is -120v. The difference between the 2 is 240v. If you use a 2 pole breaker in your breaker box and run 2 hots and a ground, you would get 240V service.
The costs for a 240V setup are pretty minimal.
A 30A 2 pole breaker will run you about $20
The cost of 10awg/3 wiring (without conduit, which type of conduit you need will depend on code) is about $1/foot.
Steel flex conduit at 1/2" (probably only big enough for 1 wire) is about $0.3/foot
From there, you can either buy an off the shelf PDU with a twist lock type connector or have an electrician manually wire up some 240v plugs. Electrical code would require him to use a different physical plug at 240v. He'd have to use a NEMA 6-15R, 6-20R, or 6-30R.. This means you'd need to order special power cables for your miners, but it's not that big of a deal to get them at $5 a pop. I'd recommend just installing a single twist lock and getting an enterprise grade PDU for $600, it'll save you on electrician costs.. And if you ever need to replace the PDU, you can do that yourself. Tripplite makes some 240V single phase PDUs. Eaton also makes some. A switched PDU starting at around $800/ea would give you remote reboot capability through a web interface. A basic PDU starting at around $200/ea would just provide the electrical distribution and maybe some power usage information (amp, volt, etc). Using the PDU, you'd also need special power cables.
The twist lock connector will cost you about $20.
For a single 240V 30A run at 300 feet which would give you a total of 7.2kW (5.76kW usable) you're looking at about $430 material cost, another $200-$800 for PDU, and whatever your electrician wants. You might want to check, in some places, home owners are allowed to do some electrical work themselves. I know a guy who did all of the electrical work for his home, which he also built himself. He was not a master electrician.
This will let you put up to around 5 ASIC miners in your mining area. I'd recommend running a separate line specifically for the cooling fans and put them on a different circuit. You could use a smaller breaker (or maybe the existing 120v line) for that.
Your house probably has a 200A or 400A main. If you wanted, you could have your electrician run multiple lines, install multiple twist locks, and for it to be possible to grow in the future without needing additional electrical work. It really just depends how many slots you have free in your breaker box. If you're planning to go heavily into mining, i'd say, run at least 2x 30A 240v lines (11.52kW usable) and use the 120v 10A line for lighting and fans... Maybe upgrade it to a 20A breaker (assuming the wire's ampacity allows for it)...
Beyond being able to run more power over the same sized lines, you'll also get around a 5% (max) efficiency increase in the PSU over 120v (your miners will use less power). The savings at 11.52kW with 0.12/KWH power costs would be around $25-35/month. There's an example efficiency curve for computer PSUs under load at 120v, 208v and 240v at this url:
http://www.apc.com/salestools/SADE-5TNQZ7/SADE-5TNQZ7_R3_EN.pdfBasic PDU with Nema L6-30P (the plug is P receptacle is R (L6-30R)):
https://www.newegg.com/Product/Product.aspx?Item=N82E16812120339&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-_-Power%20Distribution%20Units-_-Tripp%20Lite-_-12120339&cm_sp=&AID=10440897&PID=1796839&SID=277680130Switched PDU (remote reboot, remote monitoring, etc) with Nema L6-30P:
http://www.pcm.com/p/TrippLite-PDU-(Power-Distribution-Unit)/product~dpno~40780377~pdp.bceibfga...
Cooling is another story entirely...
1kW is 3412BTU/hr
11.52kW is 39306.24BTU/hr
A 3-4Ton airconditioner cools about 40,000BTU/hr, plus you need to factor in the sun hitting it, lack of insulation, etc. Then you're going to need to worry about condensation, humidity levels, and it's not insulated... Probably looking at atleast $3,000 here..
Air cooling is doable, but it depends how hot it gets on your hottest month. You'd need to do calculations there to determine heat transfer efficiency between ambient temp, and your miner temp... Then you'll need to figure out how much air you need to move to completely remove all the air in your mining area in a time frame based upon the volume of the building. A large fan installed could run you about $100-$200. You could DIY a radiator or do evaporative using tap water during the hottest months / days. Your water bill would go up but it would drop the input air temperature by 10-20 degrees or more.
Here's a DIY evaporative cooler:
https://www.youtube.com/watch?v=J_ubf0zqvSQSame principle, you just need to do the same thing on a 30,000 CFM belt fan.
Another option is to use water cooling and then build a large custom radiator external to the building -- you can find used water chillers on ebay.. But who knows how long they're going to last you before the motor or pump dies..
https://www.ebay.com/itm/Schreiber-Air-Cooled-Water-Chiller-4-Ton-7853/322908028460?hash=item4b2ed17e2c:g:8ewAAOSw7z1aHJNwI would probably go aircooling and build my own radiator.
