Last night at a friend's house I had to use a regular 120v to charge my 75D. Although tesla official number shows model x charges at 2 mile per hour using 5-15 adapter on 120v, I observed 1.5% per hour charge speed which translates to around 3.55 mile per hour. In 14 hours I managed to charge 21%, from 39% to 60%. This is much better than I expected, and I was able to do my return trip without stopping at supercharger. The car shows charging rate of 1-2 kw and 12A. Just want to provide an experience/ data point for folks who had to resort to 120v charging.