Currently, most wood pellet boiler models consider the combustion and thermal storage effects, but not the operational cycle of the boiler. This new model adds the operational states of the boiler: standby, flush, fill, ignition, stabilization, automatic combustion, burn-out, and post-ventilation states to the thermal calculations. Residential and small commercial wood pellet boiler systems can spend significant time in operational modes outside of the standard combustion modes, especially if the system has not been designed and sized correctly. Because most of the current wood pellet boiler models do not consider the other operational modes, the system performance calculations may not accurately capture the energy produced and used by the boiler system. The updated model is needed to give better feedback to the system designers concerning the efficiency of the systems as designed. The new model has been added to the TRNSYS software program and shows promise in matching measured data for wood pellet boiler performance.