  The radio emission from supermassive black holes in nearby early-type
galaxies can be used to test possible explanations for their low luminosities.
We calculate the expected contribution from thermal synchrotron emission from
hot accretion flows to the high radio frequency observations of NGC 2300, NGC
1399, NGC 4278 and NGC 4594. We find that, in all cases, and in accordance with
our previous findings, hot flows accreting close to their Bondi rates
overestimate significantly the observed fluxes. This implies that simply
assuming a low radiative efficiency for the accreting gas is not enough to
explain their low luminosities. Smaller central densities and accretion rates,
as expected in the presence of strong mass loss or convection in the flows, can
help reconcile the models with observations. We also show that a significant
contribution to the high-frequency radio spectra can be due to non-thermal
synchrotron emission from the small scale radio jets observed in these systems,
allowing for even lower accretion rates in the inflows. We suggest that these
outflows or jets may dump significant energy into the surronding medium close
to the accretion radius and so reduce the accretion rates onto these systems.
We discuss the relationship between the radio flux and black hole mass for the
observed sample and its potential importance for probing accretion models.
