One of the crucial issues of energy markets in oil exporting developing countries is the high level of subsidies on petroleum products and the low efficiency in energy use. The purpose of this paper is to investigate the impacts of a subsidy phase out policy on the energy sector and oil revenues in three countries: Algeria, Iran and Nigeria. By using a standard econometric approach, we find that the effects of different deregulation policies are substantial. We also analyse the impact of a policy based on autonomous energy-efficiency improvement. Finally, a combination of both policies is elaborated and quantified. Our results show that a policy geared at more rational use of energy would permit these countries to save enough oil to meet future increases in demand while maintaining stable production capacity. Furthermore, such an energy policy could result in additional oil revenues which would enhance their economic development.