Who cares! It's all slow right? I ordered the 5-20 adapter and put it to task today on my mobile charger at work where I plug in all day. The only way 120V makes any sense at all is if you have loooong charge times, where the car is doing nothing else anyway. I think someone has pointed this out already... but they were saying there's a fixed minimal overhead that does not go toward charging, and once you get over that, the rest goes towards charging the pack. So you effectively get more than what the 33% would suggest by going to the 5-20 adapter. Here's my data points: Power math suggests Nema 5-20 at 120V*16A is 33% more Watts than Nema 5-15 120V*12A... (set maximums allowed per adapter type). Yet, the car reports 9 kmh charge rate on the 5-20 versus 6 kmh charge rate on the 5-15. Which is a 50% improvement, at face value. If you "pessimistically de-optimise rounding", to say maybe a true 6.4 kmh is being reported as 6, and only 8.5 squeaks out of the 5-20 but shows up as a 9... then we're sitting at the 33% improvement which is closer to what the power math suggests. If you "optimise rounding" say 6 is really 5.5 and 9 is actually 9.4, then there's an argument for the Nema 5-20 being a 70% improvement. My REALITY is estimated range is climbing at 9 per hour on Nema 5-20. And it was pretty close to 6 on 5-15. So I'm seeing close to a 50% charge improvement for a plug that is taking on 33% more juice. Which seems like a good payback. Charging at a higher power is more efficient, people have said this time and time again. It's true. It all boils down to this: I used to charge all day and get a free return trip home (replenishing at work what it took to drive there). Now a round trip commute costs me just 25% of the total distance travelled. Which is a 50% savings at home on the e-bill for the commuter portion. The adapter pays for itself in 7 months if used for nothing else, at my electricity rates and what the adapter cost me. Both of which are so little ... it's a fun fact not a business case.