In the last decade, the European Union promoted several directives dealing with strategies and methodologies pertaining to buildings energy demand reduction. To accomplish fixed targets, a different design philosophy has to be adopted for new buildings construction. Additionally, RES (Renewable Energy Sources) have to be integrated as much as possible and non-invasive refurbishment interventions, matching architectural constraints for existing buildings have to be considered. This work explores the possibility to apply small scale hybrid energy systems generating electricity and high temperature heat which are compatible with typical limitations of historic buildings. To do so, six different plant layouts have been implemented, combining CHP (combined heat and power), PV (photovoltaics) arrays, PV/T (solar hybrid collectors), electric heat pumps, trans-critical CO2 heat pumps and gas heat pumps. Moreover, the potential effects of hydrogen enrichment in Natural gas, on the selected plant layouts have been investigated. Thus, all of energy scenarios have been compared each other based on four different indicators such as PFEC, building EPg (Energy, performance index), RES fraction and renewable heat. Finally, a sensitivity analysis with varying the building PTHR (Power To Heat Ratio) has been carried out in order to identify under what conditions each layout is the most efficient (C) 2017 Elsevier Ltd. All rights reserved.