This paper presents a new algorithm for calculating azimuth and altitude of the Sun from its ecliptic coordinates. The equations of the new procedure are not based on spherical trigonometry, like the procedure currently used for computing the solar vector, but on analytic geometry enriched by matrix algebra. Our proposal allows the horizontal coordinates of the Sun to be determined with a significantly higher computational efficiency than the classic algorithm without any loss in accuracy. (C) 2008 Elsevier Ltd. All rights reserved.