Dark energy and conservation of energy.

If dark energy is uniformly distributed at about 10^-8 ergs/cm3, and
the universe is expanding while the concentration of dark energy
remains the same, it means that more and more dark energy is created.

Where is this dark energy taken from? When you take energy from the
gravitational field of a black hole through hawking radiation, you
claim to be taking mass from the black hole itself.

Isn't it more reasonable to assume that dark energy is taken from the
integral structure of the universe itself, rather than to assume that
dark energy is created from nothingness?