Comment by cma

Yes it's small, but:

At least during emergence of life there was the faint young sun + higher proportions of radioactive elements, so could have made up 0.2% of outgoing thermal radiation or so on earth (ignoring outflow of residual heat from early collisions). I think 5-10 earth masses is the limit for terrestrial planets, and you can imagine having say 10x more radioactive elements and still hospitable to life, rather than being made of solid uranium. So maybe double digit percentage radiant heat outflow differences between very small and very large on those.