Cute power density factoid, which I owe to Eric Chaisson: humans have far higher power densities than stars.
The solar luminosity is about 4.10^27 W, the mass is about 2.10^30 kg; so the power density is 2.10^-3 W/kg.
Human use ~2800 kcal/day ~ 120 W. Mass is ~80 kg, so 1.5 W/kg.
Isn’t that fun?