The hope of a fast expansion of solar energy conversion by photovoltaics as a primary energy resource could be undeceived by the high production costs of PV modules. The purpose of this work is firstly to discuss both technical and economical reasons yielding the present production cost levels of 4.5 $/Wp for standard crystalline silicon technology and secondly to indicate the development path necessary to achieve a cost of 2$/Wp, which is recognised as a threshold value for an effective use of PV.