Cities across the United States are using a range of policy options to achieve their climate mitigation goals. One example is Boulder, Colorado, which has a long history of taking climate action, and is using a market-based approach to both reduce emissions and fund mitigation programs. In 2006, the city passed Initiative 202, the Climate Action Plan (CAP) Tax Initiative, which became the nation’s first directly voter-approved carbon tax. The tax charges consumers based on their fossil fuel-based electricity consumption, and the revenue is used to fund energy efficiency and renewable energy programs.