LakeLeaf:
Most vendors do not yet have UL "listed" products, so they have been skimpy with the details. Ignoring Level 3 (Quick) charging (high power, both high voltage and high current):
There are several parameters that you must evaluate to match your "needs" (and "wants"):
1. Voltage: 120v or 240v, the higher voltage is generally harder to access, and the lower is found most everywhere. However, charging rates are generally 2 to 5 times faster with the 240v connections.
2. The Charging Current: Circuits are limited by the Circuit Breaker (fuse) that "feeds" the wires. Breakers of 15, 20, 30, 40, and 50-amps are typical. Since EV charging is considered a "continuous" load, only 80% of the breaker's rated current may be used for charging (12, 16, 24, 32, 40 amps).
3. Car's Charging Current: Even when "offered" very high currents, the car is designed to have its own maximum current-usage limits. The USA model LEAF, as we expect it, will have a limit of 15 (or maybe 16) amps, and possibly only 12 amps in some conditions. Offer it more, and it will not use it. In the future, the limit will probably be double that, 30 (or 32) amps. The higher the current, the faster the car charges its batteries.
4. Delivering Current to the Car: Residential Electrical laws (NEC 625) regulate EV charging at home. Primarily, the "extension cord" from your home wiring must a special (expensive) "safety" connection, with a special "J1772" plug on the car's end, to match the "J1772" socket in the car, very reasonable. The cord's length is typically 15 to 25 feet, the maximum allowed, it seems.
5. Getting Current from the House: A "safety controller box" (an Electric Vehicle Supply Equipment (or EVSE for short) device) is required, and expected by the car, so a simple extension cord cannot be used. The EVSE can be big or small, heavy or light, ugly or not. The EVSE typically mounts permanently on a wall (hard-wired to the electrical circuit), or (more rarely) is "portable" (plugs into a wall-mounted socket).
6. EVSE Types: The 120v EVSE's are called "Level 1", are typically plug-in, limited to 12 or 15 amps, and charge "slowly", at low power. They are considered "less dangerous" to use, but 120 volts can still kill a person. The 208 to 240 volt EVSEs are called "Level 2", usually (but not always) hard-wired, higher current (typically 15 to 32 amps), and the higher power charges more quickly, IF the car can use the higher currents. The present LEAF is limited, see above.
7. Actually Charging: Assuming other loads on the circuit are not a problem (not ON while charging), the EVSE is "set" to offer the car a maximum current, "matching" the ratings of the breaker that is supplying it (16 amps for a 20 amp breaker). The car is supposed to read and respect that limit, or risk "tripping" the breaker (blowing the fuse).
Enough for now. For most people, even this is a lot to consider.
That is why Nissan arranged for a "turn-key" service for most people, to get a 240v, Level 2, 30 amp max EVSE installed in their garage (from AreoVironment), with a 3-year warranty. If AV's bidding on their installations gets "fixed" (lowest reported bid so far is $1500), it may be a reasonable solution for many folks, for overnight charging at home.
Not everybody needs the Level 2 EVSE, and the Nissan-supplied Level 1 EVSE may be sufficient for some.
Leviton and others will be offering EVSEs for purchase by year end, it seems. Here, we are waiting to hear more about the Leviton EVSEs because they might be reasonably priced, and plug-in units.
