In recent years, as a result of an important agreement with the Italian Ministry of the Environment, Lombardy Region has promoted and supported numerous measures for energy efficiency and renewable energy sources integration within its territory. Subsequently, monitoring campaigns have been launched to evaluate the global outcomes of the different calls and programs. Among other types of interventions, the promotion of the replacement of diesel boilers with high efficiency natural gas boilers represents an effective way to reduce primary energy demand and emissions and, more in general, to support the definitive transition from oil derived fuels to less polluting fuels like natural gas. The research presents the results of the monitoring ca...