Solar thermal energy is a possible technology in order to increase the renewable share inside district heating as required by European Directive 2012/27. However, these systems represent an important investment and need to be appropriately sized and operated, mainly because of the intermittency of the solar energy, to deliver heat at reasonable cost while preventing any conflict of usage between various heat producers: Combined Heat and Power (CHP), biomass boiler, solar thermal energy, etc. Exergy analysis is a promising tool to tackle this issue. To progress in that direction, this paper presents a dynamic exergoeconomic analysis on an existing solar district heating (SDH) located in the North West of France in which conflict of usage occurs. The actual configuration is implemented in Dymola and includes a large-scale solar field, a biomass boiler, a gas boiler and a thermal energy storage. Based on models available in Modelica Buildings Library, an exergoeconomic approach (Specific Exergy Costing) is implemented. Field data from year 2019 are used as input to model the demand and solar data are taken from SoDa Service. Two cases are considered: one without the solar field (reference case), and one with the solar field. This study demonstrates that adding a solar field in an existing district heating system leads to a degradation from an exergy point of view. This degradation mainly occurs during the non-heating season, when the solar energy is the source of 26% of the overall exergy destruction. It is shown that with the solar field the specific cost of the heat increases by 10% during the non-heating season. The study highlights that adding a solar field reduces the operating time of the boilers and thus increases their investment cost rates. Moreover, the solar field is the main source of extra cost, which degrades the system for an exergoeconomic point of view.