Forecast for cosmological constraints on dark energy parameters. Left: comparison of the constraining power on Ω_Λ in a flat ΛCDM cosmology from Planck 2018 alone (Planck Collaboration VI 2020) and when combined with BOSS BAO data (Alam et al. 2017). Below, constraints as obtained with BOSS voids via RSD and AP (Hamaus et al. 2020), as expected from Euclid voids (this work), and as expected from Euclid’s main cosmological probes combined (Euclid Collaboration 2020). Calibrated constraints from voids are indicated by the abbreviation “cal.” and the Euclid main probes distinguish between “optimistic” and “pessimistic” scenarios. Right: predicted constraints from Euclid voids on dark energy content Ω_de and its equation-of-state parameter w in a flat wCDM cosmology. Both the model-independent (green) and the calibrated results (red) are shown, dashed lines indicate the input cosmology. Mean parameter values and their 68% confidence intervals for the model-independent case are shown at the top of each panel.