Due to the expected growth in district heating systems in combination with the development of hybrid energy appliances such as heat pumps (HPs) and micro-combined heat and power (CHP) installations, new opportunities arise for the management of multicommodity energy systems, including electricity, heat, and gas. The possibility to "convert" forms of energy using hybrid energy appliances and exploiting flexibility from local production and consumption can improve the systems’ efficiency significantly. This paper extends existing work with a decentralized version of a multicommodity smart energy management system to deal with flexibility and scalability. The system incorporates both heat and electricity, and integrates various types of flexible appliances as well as hybrid energy appliances. To optimally allocate the available resources and its flexibility, the developed multiagent system (MAS) aims to perform optimal supply and demand matching (SDM) of the local resources and flexible appliances, as well as to flatten out the net remaining exchange over time. The proposed method is applied to a test case, where simulation results confirm that the decentralized approach leads to a scalable solution for the management of the multicommodity smart energy system (MC-SES) and performs similar to the centralized approach.