In this paper, a flexible DC load to test and evaluate current-voltage characteristics of fuel cells stacks and photovoltaic modules based on DC-DC converters is proposed. The load features are simple structure, scalability, low cost, and its possibility to emulate an arbitrary load profile. The measure of the desired characteristics of fuel cells and photovoltaic modules further includes high speed of response and high fidelity. A comparison between conventional methods and the proposed one is also provided. Experimental results show the usefulness of the DC load proposed. (C) 2010 Elsevier Ltd. All rights reserved.