With climate change becoming a certainty in the short to medium term, controlled environment agriculture will play a larger role in the production of fruit and vegetables. In such greenhouses, being able to monitor and control the environment is of upmost importance to best optimise the plants’ growth. One such parameter is the “Vapour-pressure deficit” (VPD) of the environment. VPD is the difference between the amount of moisture currently in the air, and the amount of moisture held in saturated air. If the air becomes saturated with moisture, and the leaves are below a critical temperature, water will condense and increase the likelihood of leaf rot. Therefore, it is important to maintain the VPD within a range which does not allow condensation onto leaves. To calculate VPD, air temperature, pressure and humidity must be monitored, as well as the temperature of the plants’ leaves. This project aims to develop a solar-powered sensor to monitor these parameters and report the vapour-pressure deficit using sensors and a microcontroller. Being solar powered, the system’s power consumption must be minimized, with a small battery being charged and discharged to provide power during the night.