Archival X-ray observations of EF Eridani obtained in a low state revealed distinct X-ray detections at a luminosity L _ { X } \simeq 2 \times 10 ^ { 29 } ergs ^ { -1 } , three orders of magnitude below its high state value .
The plasma temperature was found to be as low as kT \loa 2 keV , a factor 10 below the high state .
The X-ray/UV/IR spectral energy distribution suggests faint residual accretion rather than coronal emission as being responsible for the low-state X-ray emission .
EF Eri thus showed a clear transition from being shock-dominated in the high state to be cyclotron-dominated in the low state .
From the optical/UV spectral energy distribution we re-determine the photospheric temperature of the white dwarf to \sim 10000 K. Contrary to earlier claims , WD model atmospheres produce sufficient UV flux to reproduce the published GALEX flux and orbital modulation .