New to us TT with Solar system. Lots of ????'s

Another way you can look at it is, let's just say you were wiring up a new stereo system for outside your trailer and we're planning on using it on the side near the refrigerator. The stereo system would draw 160 W maximum. In this situation would you run a new power supply to the stereo or would you be comfortable with the idea of tapping into the refrigerators 12 V power supply, simply for convenience, even though it very well may be a 16 or 18 gauge wire.