The object-oriented modeling approach combines the convenience of composing system models from universal component models with the advantage of the availability of analytical system descriptions. This study describes its application to solar heating systems. The central solar heating plant with seasonal storage (CSHPSS) in Saro, Sweden, serves as an example. An object-oriented system model is developed by using the top-down approach, defining general terminals and abstract base classes first and specializing component models afterwards. System simulation results obtained with the object-oriented simulation environment OmSim are compared with results obtained with the modular simulation environment TRNSYS. Analytical system descriptions are used as the basis for numerical system optimizations.