Dependence of cluster relic radio power on a) cluster mass and b) redshift. Open circles indicate clusters hosting a pair of radio relics from the literature. Blue squares denote clusters hosting a single radio relic. Filled black (red) circles indicate the position of the SE (NW) diffuse radio sources hosted by MACS0025. The dashed red line in panel a) denotes the M₅₀₀/P_{1.4 GHz} relation from de Gasperin et al. (2014). Mass estimates are via the SZ-effect from the Planck cluster catalogue (Planck Collaboration XXIX 2014), or via a scaling relation based on the X-ray luminosity (L_{x [0.1−2.4 keV]}; de Gasperin et al. 2014) for all clusters except MACS0025, where the mass is derived in Sect. 3.3.