The mechanical difference between a NEMA 14-30 (220V 30A) and NEMA 14-50 (220V 50A) is the shape of the neutral pin (which in the case of charging a 220V car, bears no load). The 14-50 is a straight blade, and the 14-30 is an "L" shape. Some of us *cough* have been known to take our 14-50 plugs and a hacksaw and cut the blade in half, leaving only the part that fits into either outlet. If you do this, you need to be careful to always set your current down below 30A (in the car) before charging from a 30A outlet; if you forget, at best you're going to pop a breaker and at worst, you'll start a fire. Back to the OPs question -- I really *HATE* that Tesla has chosen yet another proprietary plug. They need to understand that compatibility isn't just about the car, but the charger, for the exact reason described. Why not just forgo the Tesla-brand charger and install a J1772 charger (or two) in your garage that supports the current you want and/or have available. They are available from ClipperCreek in any number of sizes. Just use the J1772 adapter that comes with the car to charge the car from these chargers (your superior Chevy doesn't need an adapter). When my Model S arrives, I'll have four different types of EV in my garage that use 4 different charging standards (none of them J1772!). I took a hacksaw to my Roadster HPC and replaced the paddle with a J1772-compatible one. I'll use this same charger for both my Roadster and Model S using their respective J1772 adapters. Personally, I don't think that the sale of a non-J1772 compliant car should qualify the manufacturer for California ZEV credits (which Tesla sells to other manufacturers).