Abstract  We discuss, from a condensed-matter point of view, the recent idea that the Poisson fluctuations of the cosmological constant about zero could be a source of the observed dark energy [1, 2]. We argue that the thermodynamic fluctuations of Λ are much bigger. Since the amplitude of the fluctuations is ∝ V ^−1/2, where V is the volume of the universe, the present constraint on the cosmological constant provides a lower limit for V that is much larger than the volume within the cosmological horizon.