Due to recent increases in electricity and fuel prices, there is growing interest in reducing energy usage in greenhouses. To reduce energy consumption in greenhouses, it is necessary to first identify the load capacity being used in the greenhouse. In this study, an energy model was designed for a melon greenhouse using Building Energy Simulation (BES) software called TRNSYS, and the cooling and heating load capacity was calculated. To design the energy model for the melon greenhouse, weather data, melon growth data, greenhouse physical characteristics, and microclimate data inside the greenhouse were used. The cooling and heating load capacity for the melon greenhouse was calculated by applying the energy exchange of sensible and latent heat in melon growth. During the growth period from 2017 to 2022, the maximum cooling and heating loads for the greenhouse were calculated to be 79,136 kJ/hr and 152,436 kJ/hr, respectively. Understanding the cooling and heating load capacity of the greenhouse will be helpful in installing the appropriate capacity of renewable energy facilities in the future.