A hybrid heat flux measurement system has been designed, built and mounted on top of the SSPS-CRS tower at the Plataforma Solar de Almeria (PSA) to measure the incident solar power that is concentrated by a heliostat field on the flat aperture of a central receiver. This device is composed of two measurement systems, one direct and the other indirect. Each direct system component, and in particular, the heat flux microsensors, which enable these measurements to be made in a few seconds without water-cooling, are described. The indirect system is based on a CCD camera that uses a water-cooled heat flux sensor as a reference for converting gray-scale levels into heat flux values. The main objective is to systematically compare both measurements of the concentrated solar power in order to increase the confidence in its estimation. At the present time, everything is prepared for heat flux measurements on the aperture of solar receiver prototypes. The incident solar power and the spatial heat flux distribution on the aperture of the HitRec II volumetric receiver are provided by the above-mentioned hybrid system. The two measurements are compared in detail showing their good agreement. (C) 2003 Elsevier Ltd. All rights reserved.