Integrated over the course of a day, total disk solar irradiance for a rotating planet is 1/4 the solar constant. And in our specific planetary case, about 27% is reflected without reaching ground. So the effective whole-day whole-Earth "solar constant" at ground level is about (1362 W/m^2) * 0.25 * (1 - 0.27) ~= 250 W/m^2.

https://en.wikipedia.org/wiki/Earth%27s_energy_budget#/media...