Three commercial photovoltaic panels based on single crystal silicon solar cells are investigated. Two types of transients are observed: instantaneous short-circuiting and instantaneous open-circuiting. It is shown that the transient currents under short-circuiting have a character of damped oscillations and the transient voltages under open-circuiting rise exponentially for all types of solar cell panels. The currently used equivalent diagrams cannot explain the results obtained. (C) 2004 Elsevier B.V. All rights reserved.