Most of studies quantified the energy technology cost of integrated urban energy systems by calculating the levelized cost of energy (LCOE), but few analyze the contribution that an individual technology can bring to whole complex systems. This study introduces a generalized “system value” approach to quantify the contribution of each individual technology to the whole system as a function of the individual’s installed capacity. A generalized urban energy system optimal design model is formulated by Mixed Integer Linear Programming (MILP). An illustrative case study is conducted to explore the system values of different urban energy technologies. The results indicate that combined heating and power (CHP) presents the largest system value among all technologies. Heating/cooling supply technologies tend to provide lower system values compared to other electricity supply technologies due to the offset effect from adoption of energy saving strategies. Additionally, an individual technology’s system value varies with different penetration levels of that technology. Overall, this study presents a formulized method to assess the contribution of an individual technology from a systemic perspective, and aims to provide a new standpoint for decision-makers (instead of LCOE) for evaluating new technologies’ integrations to complex systems.