The transient processes in six different photovoltaic panels based on single-crystal, polycrystal and amorphous solar cells are analyzed. Two types of transients, arisen because of instantaneous changes in load, are investigated. The transients analyzed are: (a) an instantaneous short-circuiting from an open circuit condition and (b) an instantaneous open-circuiting from a short circuit condition. Different characters of transients are observed. The character of the instantaneous short circuit processes for all panels is damped oscillations. These oscillations are characteristic of a second order circuit, whereas the instantaneous open circuit process takes for all panels the form of an exponential growth that is characteristic of a first order circuit. The similarities and differences of results obtained for the different panels are compared, analyzed and discussed. (c) 2006 Elsevier B.V. All rights reserved.