Bluetick1010

WACC is the weighted average cost of your existing capital.
If you still have earnings --> it is your margincal cost of cap.

If you have used up your retained earnings (i.e., run out of internally generated cash and need new external cash) --> you have to go outside and get new investors/borrow, then your marginal cost of cap is whatever the return theNEW investor requires.
Your WACC will be calculated anew taking in the weight and return of the new cap.