Fast Radio Burst Energetics: A Census of Isotropic-Equivalent Energies and the Volumetric Power Budget

We compute isotropic-equivalent radio energies for six well-documented fast radio bursts (FRBs) with spectroscopic host-galaxy redshifts — the repeaters FRB 20121102A, FRB 20180916B and FRB 20190520B, and the apparently non-repeating FRB 20180924B, FRB 20190102C and FRB 20190608B — using published fluences and a single stated bandwidth convention of 400 MHz. The resulting energies span 3.55 × 10^37 erg to 1.84 × 10^40 erg, a factor of 519, with the apparently non-repeating bursts occupying the high-energy end of this small sample. Combining the volumetric rate of Shin et al. (2023), 7.3 × 10^4 Gpc^-3 yr^-1 above 10^39 erg, with the mean energy of their Schechter energy distribution above that threshold, 2.34 × 10^40 erg, gives a volumetric radio energy generation rate of 1.70 × 10^45 erg Gpc^-3 yr^-1. This is 2.4 × 10^-11 of the core-collapse supernova kinetic power density and 1.5 × 10^-6 of the rate at which magnetic energy is created in newborn magnetars with internal fields of 10^15 G. In radio emission alone the FRB population is therefore an energetically negligible draw on every known reservoir; the budget becomes restrictive only when a low radio efficiency is imposed. For the repeaters, a 10^4 yr active life at duty-corrected observed burst rates costs FRB 20121102A 4.32 × 10^46 erg in isotropic-equivalent radio energy, 26% of the total magnetic energy of a magnetar with a 10^15 G internal field and 0.26% for a 10^16 G internal field. Beaming is treated throughout as an explicit correction, stated separately and never folded into the quoted energies.