It is well known that electrical output parameters of photovoltaic solar cells and modules are dependent on the angle of incidence of the solar radiation. Angular effects can be described in brief as a reduction on the device output parameters when light impinges at angles diverging from the normal to the surface, affecting the accurate calibration of radiation sensors and introducing energy losses in photovoltaic conversion. This paper is focused on the measurement of the angular response of solar cells based on different silicon technologies, and on the analysis of the sources of deviation from the theoretical response, especially those due to the surface reflectance. As main contributions, the effects of encapsulation on the angular response of the modules are investigated by comparing bare and encapsulated cells, and analytical equations describing the angular behaviour of cells' short-circuit current, open-circuit voltage and maximum power, including the reflectance of the structure, are derived. (C) 2004 Elsevier B.V. All rights reserved.