Annual simulations of combined solar and pellet combisystems have been performed based on measurements of two pellet boilers and a burner integrated into a solar thermal energy storage (TES). The results show that the investigated burner integration is more energy efficient in comparison with the external pellet boiler solution. The flue gas losses were the predominant losses measured for steady state burner operation, but heat losses to the ambient were predominant in the annual simulation results. The number of ON/OFF cycles of the pellet burner depends to a high degree on the control strategy implemented to adapt the power modulation to the current demand, and varied from almost 3000/a in the worst case to less than 900/a in the best case simulated. Based on parametric simulation studies, it was determined that the fractional energy savings of both systems could be increased fromaround 20% to 30% for a house with 4.6 kW heat load at climate Zurich without increasing the area of 10 m2 flat plate collectors or the TES volume of 850 litres. A comparison with a hypothetical TES of the tank-in-tank design showed additional potential for improvement due to a smaller area of the TES that has to be kept at high temperatures for DHW use.