  We present a method based on the so-called Quantum Energy Inequalities, which
allows to compare, and bound, the expectation values of energy-densities of
ground states of quantum fields in spacetimes possessing isometric regions. The
method supports the conclusion, that the Boulware energy density is universal
both: at modest (and far) distances from compact spherical objects, and close
to the would-be horizons of the gravastar/QBHO spacetimes. It also provides a
natural consistency check for concrete (approximate, numerical) calculations of
the expectation values of the energy-momentum tensors.
