I was looking over the J1772 standard I found at:
http://wenku.baidu.com/view/8d35b7d0496 ... 747b5.html
and it turns out the pilot signal from the EVSE to the EV charger tells the charger how much current it may try to draw. The pilot tone of 1KHz besides defining the coupler state also has a duty cycle which defines the EVSE current capacity.
Up to about 85A, the formula is %duty cycle x .6 = capacity in Amps.
So if the 1KHz pilot tone has a 20% duty cycle ( 20% on and 80% off ), it means the EV charger may draw 12A. If the EVSE was plugged into a 15A circuit ( or didn't know ), it would tell the EV charger to only draw 12A. That keeps the load current at the NEC 80% level.
On the other hand if someone installed the Level 1 EVSE with a dedicated 20A circuit, the EVSE should have the feature of sending the pilot tone at 26.67% which says the charger may draw 16A or 80% of the 20A circuit. The same would be true for the Level 2 where a 32A EVSE circuit would send a 53.3% duty cycle,while a 50A circuit could draw 40A = 80% which would be indicated with a 40/.6= 66.7% duty cycle.
So why is this important? It means the SAE standard allows both 15A and 20A Level 1 circuits and additional currents above the 32A from the AV EVSE. That means if you wanted to wait and use the Level 1 charger until the prices came down on the Level 2, you could buy a level 1 that had this feature and reduce your charging time by roughly the current ratio if you had a dedicated 20A circuit. Forgetting charger and battery losses for the moment, a 24KWHr battery requires 120V x 12A = 1440VA = 16.67 hours to charge.
Also ignoring the inefficiency in charging for the moment, 120V x 16A = 1920VA = 12.5 hours to charge. That's the difference between overnight and being short of overnight when one takes inefficiencies into account.
Hopefully someone will come out with a Level 1 EVSE that allows this feature so it's practical to wait for a cost effective Level 2 EVSE to arrive as volumes and competition arise. There are many companies designing EVSEs so it shouldn't take long before one can buy it yourself and install it yourself or hire and electrician to do it and not have to be forced to go with AV.