Various trade-offs in the design and system selection of wood fired systems are discussed. Importance of base load concept of system design is emphasized. Most important design factors are described. These are divided in two groups, i.e., site specific and system specific factors. The first group includes annual heat consumption, load characteristics, fuel cost, heating system, etc. System specific design factors include fuel type, feeding system, boiler type, layout, etc. Alternative designs and their economics are presented. Different layout schemes are illustrated. Results of six feasibility studies on wood conversion of existing space heating systems to wood fuel are described. It was discovered that conversion of a heating system to wood fuel becomes feasible when the existing annual heating energy costs more than $15,000.00.