The Karma will only

*draw* 3.3 kW from the charger. At 240 volts, that's 13.75 amps. Though technically it can draw up to 18 amps for some periods (the 3.3kW is the average charge rate into the car, vs what comes out of the wall socket, there are some losses and minor peaks and valleys) and some Leaf cars will charge at 3.84 kW (16 amps).

You would think a 20 amp circuit would suffice. It turns out that a "20 amp" circuit is only rated at 16 amps continuous (80% of the label), which is enough. But I've been told that it's better to get a standard electric dryer 30 amp circuit put in. Any electrician will understand this ("a standard 30 amp electric dryer circuit" = "sure!", "a 30 amp car charger circuit for my expensive exotic car" = "uh... I've never done one of those, maybe you should get someone else" from some electricians), and it should be cheap, as such things go.

On the other hand, if you intend to charge a newer 6.6kW Leaf, you might want to go with a 40 amp circuit. That's a pretty standard electric range circuit, to an electrician.

(If you're getting a Tesla Model S it can take whatever you can afford to throw at it: 50, 70, even 100 amps. 50 amps is the largest standard electric range circuit—as far as I know anyway—and if you go beyond that you might start to need an electrician who really knows what he's doing.)

See the

"charging and chargers" forum and especially

this post musing on attempts to upgrade to 6.6kW charging.