We develop an economic partial equilibrium model for energy supply and demand with capital and labor as production factors, and endogenous technological change through learning by research and learning by doing. Our model can reproduce the learning curve typical for (bottom-up) energy-system models. The model also produces an endogenous S-curved transition from fossil-fuel energy sources to carbon-free energy sources over the coming two centuries. We use the model to study carbon taxes' effects on fossil-fuel and carbon-free energy use and carbon dioxide emissions. It is shown that without induced technological change, carbon taxes have a modest effect on emissions, while with induced technological change, they accelerate the substitution of carbon-free energy for fossil fuels substantially. © 2005 Elsevier B.V. All rights reserved.