It is increasingly being realized that by affecting geoeffective scale lengths the interplanetary electric field (IEF) is a key quantity in space weather discussions. In this work we derive and analyze statistically IEF coherence lengths in year 2000, i.e., near maximum of solar cycle 23, working in a much used formulation for the IEF. We focus on the frequency domain. We use magnetic field and plasma data sets acquired by Wind and ACE. During year 2000, ACE‐Wind separations were very variable and, in particular, Wind’s first dayside distant prograde orbit resulted in a Y‐separation comparable to the X‐separation (∼220RE). We find IEF coherence lengths of 200–250RE(X) and 50–100RE(Y). The coherence is mainly carried by the low frequency components (f< 0.01 min−1). © 2003 American Institute of Physics