On it's near parabolic rise, Tesla did not rest and form many areas of key support. Now that we're starting to see a retrace, I drew up some key levels where Tesla is likely to find buyers.
Key support levels are areas where there have been strong reactions in the past. This does not mean that the price will bounce from these levels, it just means that there are other people looking at these levels as they are fairly obvious to many technical analysis traders. If you're looking to add to your position, I think the orange trend line around $550 is a decent bet. If that doesn't hold, ~$500 seems like the next decent area of entry.