Abstract The integration of significant shares of renewable energies poses remarkable issues related to the intermittent nature of these sources. Nonetheless, solutions in support of renewables integration exist and become particularly effective if conceived under a smart energy system perspective, to exploit potential synergies among different energy sectors. With this respect, shifting programmable consumption from fossil fuels to electricity represents one measure to exploit otherwise-curtailed renewable generation. In this study, the impact of electrification of both private transport and space heating is assessed for the Italian energy system with the help of EnergyPLAN software and quantified in terms of critical environmental and techno-economic indicators, evaluating to what extent increasing the electricity demand supports the development of renewables. Results confirm that both transport and heating electrification can lead to significant reductions in CO 2 emissions, around 25–30% if pursued independently. However, smart charge allows managing transport electricity demand more flexibly than heating demand, which makes the former more effective than the latter in fostering an increased renewable penetration, unless additional technologies are deployed to enhance flexibility in the heating sector. A techno-economic optimisation identifies possible optimal scenarios capable to reduce emissions by up to 47% with an increase in annualised costs of 34%.