In this work, we studied the performance of the temperature control system of an anaerobic digester heated by solar energy using the hardware in the Loop (HIL) simulation method. The implemented control type is On/Off. The main objective was to implement the control to maintain the temperature between 36°C and 38°C. We also aim to determine the minimum load of the digester which allows minimum stress on the control system in order to increase its service life but also to avoid being too dependent on temperature variations in the study environment. It appears at the end of this work that the temperature is well maintained between 36°C and 38°C, for all the quantities of organic matter studied. For small volumes (less than 1,000 Kg), the bias of the heating system actuator is significant.At best, (that is, for 1,000 Kg) we have on average 5 per day. This causes the heating system to be more dependent on the availability of solar radiation. On the other hand, from 3,000 Kg of organic matter, the temperature of the digesterstabilizes better in the desired temperature range. The bias of the heating system is lower, ranging from two (2) per day for 3,000 Kg to one (1) per day for 10,000 Kg of organic matter.