It can be shown that the surface area of a cylinder is minimum when height=diameter.
Calculus is one of the easiest to do this with. It's not too bad.
Here is a general case, then you can use whatever V you wish.
Assuming it has a top and bottom:
Solve  for h and sub into :
Set this to 0 and solve for r and we get
Sub into  and find
See?. h is twice r just as was stated in the beginning.