Saturn's moon Titan could harbor life, but only a tiny amount

I'm interested that their conclusion -- that Saturn could only support tiny life forms such as bacteria -- is not dependent in any way on the distance from Titan to the Sun.

Am I wrong in thinking that any life must require a steady input of energy, and that this must come from either solar energy or geothermal energy? Quick Googling says that Titan's core isn't known for sure, but probably isn't very hot.

If Titan's life were dependent of solar energy, wouldn't it's distance from the Sun imply very little energy to go around, and so very unlikely to have large organisms?