A while back I found 15-19% voltage drop in a new construction. If that high I feel obligated to report it. And did. Builders electrician called freaking about the solution. He admitted he used Stab type receptacles. They also had screws so I told him to try an experiment and switch to the screws. He seemed reluctant. It was also a 4000 sq ft house and length of run may be an issue as he ran all #14 wire.
Builder called complaining a couple of times and I told him more and more HI would be testing with the Sure test. In the end the builder called and said he and electrician learned something and in the future will not use stab type receptacles and on long runs use #12 wire.
Voltage drop is a Fine Print Notes issue in NEC. Not enforceable but fine print says 5% drop will provide reasonable efficiency of operation.
As Jerry Peck says to his clients something like Will you be satisfied without reasonable efficiency of operation? Or Mr quality builder are you happy without reasonable efficiency of operation? Here is a good link.
http://www.mikeholt.com/documents/ca...oltageDrop.pdf