An analytical model, based on basic heat-transfer processes within a greenhouse, was used to study the performance of heat pump to meet the heating and dehumidification requirements in a greenhouse. Performance parameters of the heat pump, namely the Coefficient of Performance (COP) and the Specific Energy Consumption (SEC) of the heat pump were determined, along with the condenser and evaporator capacity ratings required to provide the necessary thermal conditioning to a model-sized greenhouse. Based on a typical weather pattern in Bangkok, the performance of the heat pump to maintain the greenhouse air at a day temperature of 27degreesC and night temperature of 18degreesC with a relative humidity of 40% spans 1.2-4.0 and 1000-16,000 kJ/kg for COP and SEC, respectively. (C) 2003 Elsevier Ltd. All rights reserved.