Even at the center of the sun's core, the power density doesn't go above 300 W/m^3. At the core boundary it's < 10 W/m^3, and it's < 2 W/m^3 overall. Terrestri

Even at the center of the sun's core, the power density doesn't go above 300 W/m^3. At the core boundary it's < 10 W/m^3, and it's < 2 W/m^3 overall. Terrestrial reactors try for much higher reaction rates. But most designs still have power density issues that would make them uneconomical even if they could make net power. Net power is actually a very low bar, corresponding to an EROI of 1.