Solid oxide fuel cell (SOFC) power generators can now be commercialized as heat and power micro-cogenerator. Few well-documented field tests have been conducted to date on these units' tubular cell architecture, however, and little has been done to derive general rules for a thorough understanding of these units' operation. The present work focuses on characterizing the hydrogen-powered Acumentrics Gen521 (rated 2.5 kW) under various stable conditions. A test rig was installed at the Dipartimento di Energetica of the Universita Politecnica delle Marche (Ancona, Italy) to ascertain the main characteristic curves of the Acumentrics Gen521. A multivariate data analysis was performed on the experimental data collected to establish the operating parameters most influential for the stack voltage (SV) and the DC stack output power generated in different working conditions. Some multi-linear response surfaces are suggested for predicting the SV and the DC power in different operating conditions. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.