We examine integration of pricing and regulatory policies in the abatement of energy-related CO2 emissions. Price-equilibrium models gauge the response of energy users to changing prices and are therefore appropriate for evaluating the impacts of carbon taxes. Technology-cost models estimate the level of energy use and carbon emissions that would arise given full implementation of cost-effective energy-efficient technologies and therefore capture the potential to reduce emissions through non-price regulatory measures. If market failures impede the adoption of cost-effective carbon-abatement technologies, achieving emissions reductions at minimum social cost requires the joint implementation of pricing and regulatory instruments.