fordman
I'm sure you would be OK going as far as 100 ft from the xfmr. If you are going any further then increase the size of the wire that is supplying the voltage to the lights.

RT
Besides the wire gage used it depends on amps and watts used. A solar panel charges the batteries at our cabin; 2 12v HD truck batteries, and we have all the 12v lighting we need and we have a converter and get about 6 hours of 110v power from 2 batteries putting out a 12v charge.