A global clean energy transition is required for achieving ambitious climate goals and ensuring sustainable development. While technological advancements are crucial, they are not sufficient on their own to meet Paris Agreement (PA) climate targets. Integrating lifestyle changes, particularly in sectors such as transport and residential use of energy, into climate policies and energy modeling framework is gaining recognition in energy transition research. This study explores the impact of lifestyle changes on the global energy system and CO2 emissions using the PROMETHEUS model, an advanced energy–economy–environment system model. In this research we present scenarios in which lifestyle changes, such as reduced private car use and increased adoption of public transport and energy-savings behavior in households, are gradually introduced and complement technological and policy measures within the energy transition framework. We explore the impacts of scenarios with different levels of climate policies and lifestyle changes to evaluate the effects of various behavioral shifts on global energy consumption and CO2 emissions. Results show that even under current climate policies, lifestyle changes can reduce global energy demand by 5% by 2030 and 10% by 2050. When combined with ambitious decarbonization policies, the reductions are much more significant, leading to a 35% reduction by 2050 compared to the baseline scenario. Overall, the findings suggest that lifestyle changes, when effectively integrated with climate policy measures, can reduce energy demand and carbon emissions, alleviate the pressure on energy supply, and reduce the cost burden for energy producers and consumers.