  Circuit models involving bulk currents and inductances are often used to
estimate the energies of coronal magnetic field configurations, in particular
configurations associated with solar flares. The accuracy of circuit models is
tested by comparing calculated energies of linear force-free fields with
specified boundary conditions with corresponding circuit estimates. The circuit
models are found to provide reasonable (order of magnitude) estimates for the
energies of the non-potential components of the fields, and to reproduce
observed functional dependences of the energies. However, substantial departure
from the circuit estimates is observed for large values of the force-free
parameter, and this is attributed to the influence of the non-potential
component of the field on the path taken by the current.
