As for US residential powerlines... this should be a major design concern for Bitmain or any other miner mfgr because PSU's do NOT like low lines... In Detroit area home power is 110v - not 120 - and during summer will often drop to 100-105v. The '220v' incoming reflects the same drops. This year it got so bad (hit 95v for 2 weeks) I had to wire in a boost transformer to make up the difference...
I'm not sure anything can be done for that. The vast majority of the market doesn't have that problem, and one which will affect all electronics.
'All electronics' - and more. Gas clothes dryers and stoves did not want to work either because the igniters would not come up to temp...
In this instance the problem only really affects PSU's being pushed to near max output. What to be done? Easy answer, appropriately de-rate the PSUs like HP did with their CS server PSU's so it
can run on a low line and still produce required power. Then it is just a matter of balancing cost/benefit. Frankly, given how vocal folks can be here when there is an issue I'd err on making sure they can go down to at least 100v to cover wiring in old homes & apartments.
1400w miners aren't designed for old homes and apartments, and its not fair to make every customer pay another $20 a unit for that small minority. Frankly I'm surprised your derating problem is even legal in the US.
Maybe, maybe not. A lot of places in the world suffer from brownouts which can bring voltage plummeting down to ~90v. For anywhere in Canada/USA to be a constant 100v instead of 120v to me is ridiculous. Detroit is a special situation though, I suppose.
I'm fortunate enough to have one of the best electrical utility companies in the world (Hydro Quebec) servicing me, so I don't have to worry about low voltage situations. I draw a constant ~100-120A from my 200A home electrical installation, and still show 118v/236v at the wall. That being said, I would gladly pay an extra $20 per miner if it meant having an actual quality PSU in the unit. When it comes down to it, these high wattage power supplies almost have enough current to arc weld. I have absolutely no faith in a no-name Chinese power supply company, and my worries were proven right with the S4. I don't care if it's made in China, as long as it caries a known brand name with specs and reputation that I can look up. I'll pay extra every day if it means getting a hassle free PSU from the likes of Seasonic, Flextronics, Delta, Super Flower, etc. Apluspower Co. doesn't inspire any faith at all, and is a fire hazard in my books.
I'd like to believe that the revised power supplies from B2 will solve the issue, but there have already been reports of burnt out/DOA PSUs. I'll be replacing mine with 2000w Deltas to be safe, and when I sell them they will still have working OEM PSUs.