The pellet consumption for single family house heating in Sweden is increasing strongly. Pellet stoves and boilers for domestic heating are becoming increasingly popular and new stove models with gas-liquid heat exchangers have entered the market. There is a need for computer models of the stoves, in order to perform simulation studies. The objective of this work was to evaluate pellet stoves and to make mathematical models of them for use in simulations of heating systems with TRNSYS. Three pellet stoves, one traditional and two with gas-liquid heat exchangers, and one pellet burner were tested in a combustion laboratory. A mathematical two-node model of a stove was developed and implemented as a TRNSYS component. A number of heat transfer coefficients and thermal masses of the stoves were identified. The calculated performance of the stoves agreed well with the measured data. The stove model was used in extensive TRNSYS simulations of yearly performance of single-family house heating systems. The simulations showed that the emissions, the yearly efficiency of a stove and the savings of auxiliary electric energy for heating may vary significantly depending on system design and control strategy.