An investigation into the effectiveness of phase change material (PCM) panels placed against the internal walls of a freezer to maintain stable temperatures in the presence of heat loads such as door openings, defrosting, and loss of electrical power was carried out. Temperature response was studied during loss of power, a defrost cycle lasting 30 min, and a door opening scheme of 13 door openings over an 11 h period. This PCM system has significantly decreased the rate of temperature increase inside the freezer during defrosting and power loss. Energy consumption was measured during steady operation, a defrost cycle of 30 min, and a scheme of eight door openings at 40 min intervals. It was found that heat loads caused greater energy consumption, and that the presence of PCM during defrosting and door openings resulted in slightly lower energy consumption compared to without PCM. (C) 2010 Elsevier Ltd. All rights reserved.