Saturn is about 10 times further from the sun. Solar radiation being proportional to the square of the distance, that means Saturn would receive 1% as much as on Earth. I guess it's feasible with large solar panels.
Mars would get about half, and Venus around double based on their relative distances from the sun.
The Cassini probe probably only requires a fraction of a Watt of energy, something really puny. So that 1% would do it for a small probe, but for a colony, not sure.