Integrated Energy Systems (IES) are essential for achieving efficient and sustainable energy solutions. This thesis introduces a bi-level mathematical optimization framework that aims to balance energy providers’ profitability with consumer cost savings. At the upper level, the energy provider (leader) maximizes profit by optimizing revenues and costs while offering competitively priced bundled energy services. At the lower level, consumers select the most cost-effective bundles to minimize their expenses while meeting their energy needs. This hierarchical structure fosters a mutually beneficial dynamic—providers enhance profitability, while consumers reduce energy costs. The model incorporates key factors such as energy prices, demand variations across user groups, and multiple energy sources (electricity, gas, and hydrogen) while integrating Photovoltaic (PV) systems, Combined Heat and Power (CHP) systems, and Gas Boilers (GB) to enhance flexibility and sustainability.