This paper argues that a hypothetical “dark” particle (a black hole with the reduced Planck mass and arbitrary temperature) gives a simple explanation to the open question of dark energy and has a relic density of only 17% more than the commonly accepted value. By considering an additional near-horizon boundary of the black hole, set by its quantum length, the black hole can obtain an arbitrary temperature. Black-body radiation is still present and fits as the source of the Universe’s missing energy. Support for this hypothesis is offered by showing that a stationary solution to the black hole’s length scale is the same if derived from a quantum analysis in continuous time, a quantum analysis in discrete time, or a general relativistic analysis.