Level 1 goes up to 20A. It's unique in not requiring any special safety features over a standard NEMA outlet, because it basically *is* a standard NEMA outlet.
Level 2 J1772 goes up to 80A (19.2kW). But most chargers (both the offboard and onboard hardware) don't support currents that high, and that includes the Leaf. The Leaf is limited to 3.3kW, although there's been some talk of it possibly going to double that, perhaps as an option (that's an option I'd definitely take; it'll let you make good use of 50A RV sockets if you get a J1772 adapter).
Level 3 is 480VAC in, generally, and variable DC out, and since there's no standard for the US yet, there's no official upper bound, and level 3 chargers as powerful as 300kW have been built. The Leaf, however, is limited to 50kW.
Level 4 is even rarer than Level 3. An example is the 800V, 1000A Aerovironment (yes, 800kW!) charger they sold to TARDEC. No commercial EV that I have heard of, in service or proposed, will support this in the coming years. In the far future, I hope to see semis running off these.
The lower end of Level 3 can run straight off the grid, although utilities don't like it. The upper end of Level 3 and all of Level 4 should be run with a battery buffer, or you're going to have some very angry utilities (and their consumers). Level 3 and 4 chargers are large and quite pricey. A 250kW charger is the size of a vending machine, while the 800kW charger is the size of four vending machines shoved together. I've not seen any prices for the Nissan/Aerovironment 50kW chargers, but judging from historic prices, I'd expect them to run about $40k a pop. The price doesn't scale linearly; if I recall, a 250kW Level 3 charger will run you about $130k (w/o a battery bank). In an ideal future-charging scenario, each Level 3 or Level 4 "charging area" will share a common, large battery buffer and have half a dozen or so chargers. They'll probably do what Aerovironment currently does on a number of their chargers, which is having two or more charge connectors per charger, and if you have one vehicle, they charge at the max rating, while if you have multiple, the current gets split up between them.
Last edited by KarenRei
on Thu Apr 29, 2010 6:01 pm, edited 2 times in total.