In this study, three solar and pellet heating systems have been studied with the help of monitoring system. The main technology of these three systems is generally the same. The main target system is located in Hedemora which has an extra shunt loop in the boiler circuit. The following data have been monitored during this period: the solar irradiation, the outdoor and indoor temperature, the return and supply temperature of each circuit, the flow rate of each loop, the 3-phase and 1-phase electricity consumption. The aim of this thesis work is to evaluate the thermal performance of the system and through analysis of the detailed data find whether each component of the system functions as it should do. Also the main ambition is to make some improvements based on analysis of the one minute step monitoring data. The whole system can be divided into four different circuits: solar collector circuit, DHW circuit, space heating circuit and boiler circuit. In the process of study, a special excel sheet should be used to calculate the energy balance and operational curve of each component. In general, we found that the monitoring result varies with design setting. And more heat losses have been found in the process of the operating. For a two person detached house, ten square meter solar collector and 750 litres buffer store are both oversized. Based on these findings, in the future work, more simulations are needed. To pursuit more efficiency thermal performance, some temperature setting of the control system should be changed.