Abstract:
Estimates of marginal abatement costs for reducing carbon emissions derived from major economic-energy models vary widely. Controlling for policy regimes we use meta-analysis to examine the importance of structural modeling choices in explaining differences in estimates. The analysis indicates that particular assumptions about perfectly foresighted consumers and Armington trade elasticities generate lower estimates of marginal abatement costs. Other choices are associated with higher cost estimates, including perfectly mobile capital, inclusion of a backstop technology, and greater disaggregation among regions and sectors. Some features, such as greater technological detail, seem less significant. Understanding the importance of key modeling assumptions, as well as the way the models are used to estimate abatement costs, can help guide the development of consistent modeling practices for policy evaluation.

Abstract:
This paper develops analytical and numerical models to explain and estimate the welfare effects of raising Corporate Average Fuel Economy (CAFE) standards for new passenger vehicles. The analysis encompasses a wide range of scenarios concerning consumers valuation of fuel economy and the full economic costs of adopting fuel-saving technologies. It also accounts for, and improves estimates of, CAFE's impact on externalities from local and global pollution, oil dependence, traffic congestion and accidents. The bottom line is that it is difficult to make an airtight case either for or against tightening CAFE on pure efficiency grounds, as the magnitude and direction of the welfare change varies across different, plausible scenarios.

Abstract:
Some studies of renewable portfolio standards find that regulations increase electricity generation costs; others find that the reduced demand for nonrenewable energy sources lowers natural gas prices and that electricity prices follow. This paper presents reasons for why these predictions can vary in the direction as well as the magnitude of their effects. The two driving factors are the elasticity of electricity supply from renewable energy sources relative to nonrenewable ones and the effective stringency of the target. The availability of other baseload generation helps to determine that stringency, and demand elasticity influences only the magnitude of the price effects, not the direction of those effects. The paper also evaluates circumstances under which higher standards can decrease both certificate prices and renewable energy supply. Sensitivity analysis indicates that assumptions about renewable energy supply slopes are more important than those about nonrenewable supplies in predicting the retail price impacts of renewable portfolio standards.