This does bring up an interesting point. The Level 1 EVSE itself does not have any mechanism to limit current nor know whether its plugged into a 15A or 20A outlet. The charger inside the EV will decide how much current it wants to draw. The EV will know whether its a Level 1 or Level 2 EVSE but not what the circuit capacity actually is. Its a shame not to have the EV programmable such that it could be configured for 80% of 15A or 20A so it charges as fast as practical given the charging source circuit. Both 120V and 240V can have different source circuits if they are hardwired. 120V @ 15A x .8 = 12A is the safest route but also the slowest charge. Does the Leaf provide any kind of charge current programmability?
Its too bad the EVSE can't communicate to the EV, its source current capacity, if it knows. If its hardwired it could let the EV know for Level 1 or Level 2 and if it doesn't know, the EV falls back to the minimums of 12A for 120V and 32A for Level 2. It would be simple to implement in the pilot pin interlock mechanism. Moving from 12A to 16A for Level 1 which is by far the most common available, would make a significant difference. It could make the difference between squeezing in a charge overnight at 12 1/2 versus 16 2/3 hours roughly ignoring losses.