Performance of a hybrid heating-system, combined with thermal storage using shape-stabilized phase-change material (SSPCM) plates, is investigated numerically. A direct gain passive solar house in Beijing is considered, which includes SSPCM plates as the inner linings of walls and the ceiling. Unsteady simulation is performed using a verified enthalpy model, with a time period covering the winter heating-season. Additional heat supply is employed during load hours at late night and early morning (23:00-07:00 in Beijing) or during the whole day necessary to keep the minimum indoor air temperature above 18 degrees C. The results indicate the thermal storage effect of SSPCM plates, which improves the indoor thermal comfort level and saves about 47% of normal-and-peak-hour energy use and 12% of total energy consumption in winter in Beijing. (c) 2006 Elsevier Ltd. All rights reserved.