PLEXOS power system optimisation tool was used to model Italian power system and analyse several scenarios to optimise and increase flexibility in the system by 2030. The results show a clear value for flexibility: adding 5-7 GW of flexible gas generation enables better integration and utilisation of renewable energy sources. The fast start and stop capability of flexible gas generation enables operation of the units only when needed, thereby fully supporting intermittent renewable generation. Better utilisation of renewable energy and non-spinning reserve provision enables 400 MEUR savings in annual system costs as well as increased renewable energy penetration and reduced CO2 emissions.