 How can IAEA tools help countries make smart energy choices? Energy is vital for all human activities. It powers economic and social development. The world faces major challenges in ensuring access to modern energy services. But today, almost one billion people have no access to electricity, especially in rural areas. Because of growing populations, by 2030 an additional one billion people will need electricity. Some countries are rich in natural energy sources, some are less lucky. Different energy sources have different environmental impacts, but the challenge remains how to reduce the impact of energy production on health and the environment. Today, 70% of the world's electricity comes from burning fossil fuels, but a transition to a low-carbon energy system is necessary for reaching sustainable development and climate change mitigation goals. How can countries address all these issues and plan ahead? The IAEA assists member states in charting out their energy strategies. About 150 countries and 20 international organisations use IAEA's analytical tools for sustainable energy planning. These tools help assess energy systems. They help to organise data, analyse future energy demand, develop energy supply strategies, plan power sector expansion, explore energy scenarios, analyse project finances, investigate environmental impacts. With or without interest in nuclear power, IAEA modelling tools are helping countries make smart energy choices for building a sustainable future.