A simple analytical model of the non-Maxwellian electron velocity distribution, whose parameters are constrained by the observed plasma current and soft X-ray emission spectrum, is used in conjunction with a fully three-dimensional ray tracing code to calculate the absorption of radiation in the electron cyclotron range of frequencies by WT-2 discharges. This gives a quantitative, theoretical description of the way in which a drifting population of energetic electrons appears to dominate WT-2 current drive experiments. Calculation of the proportion of source power absorbed by the plasma helps to determine the efficiency factor of the current drive mechanism in this context. The strong dependence of current drive on the extraordinary mode launch direction is given theoretical support.