In the coming decades the energy sector will have to face three major transformations concerned with climate change, security of supply and energy poverty. The first two have been extensively analysed, but less attention has been paid to the third, even though it has a great influence on the lives of millions of people. This paper presents an overview on energy poverty, different ways of measuring it and its implications. According to the WHO, indoor pollution causes an estimated 1.3 million deaths per annum in low income countries associated with the use of biomass in inadequate cookstoves. Although energy poverty cannot be delinked from the broader, more complex problem of poverty in general, access to energy infrastructures would avoid its most serious consequences and would help to encourage autonomous development. According to the IEA, the cost of providing universal access to energy by 2030 would require annual investment of $35 billion, i.e. much less than the amount provided annually in subsidies to fossil fuels. Finally, the paper argues that energy and energy poverty need to be incorporated into the design of development strategies.