This paper presents an analysis of operational parameters of the commercial Organic Rankine Cycle (ORC) cogeneration unit integrated with biomass-fired boiler and municipal heating network. The analysis is based on field measurements in real operational conditions using standard industrial sensors installed within the system. Regression based mathematical modelling have been applied to develop robust predictive models of the ORC system for its diagnostics and production planning. Historical data collected within the Supervisory Control and Data Acquisition System of the plant have been used to establish correlations between key thermodynamic parameters. Results reveal off-design performance characteristics of the ORC unit and its individual components such as turbine, evaporator and condenser. There are also demonstrated results of application of the model for technical condition and performance monitoring, which can support decisions on maintenance activities. (C) 2019 Elsevier Ltd. All rights reserved.