I will agree with Reno- Stay away from the street lighting. I know it seems to be the easy fix but I still think its a bad idea. In my area a lot of the street lighting is 277 volt. They are usually wired on a 3 pole breaker. 1st pole uses phases A & B- 2nd pole uses phases B & C - 3rd pole uses phases C & A. Then it gets repeated this way. It keeps everything pretty balanced.
I think the best way is to run a large conduit and figure on pulling a large enough wire for a 100 amp sub panel. You may only use 20 amps now but in the future ...
