Energy tax policy involves the use of one of the government's main fiscal instruments, taxes (both as an incentive and as a disincentive) to alter the allocation or configuration of energy resources and their use. In theory, energy taxes and subsidies, like tax policy instruments in general, are intended either to correct a problem or distortion in the energy markets or to achieve some economic (efficiency, equity, or macroeconomic) objective. In practice, however, energy tax policy in the United States is made in a political setting, determined by fiscal dictates and the views and interests of the key players in this setting, including policymakers, special interest groups, and academic scholars. As a result, enacted tax policy embodies compromises between economic and political goals, which could either mitigate or compound existing distortions. U.S energy tax policy as it presently stands aims to address concerns regarding the environment as well as those surrounding energy security. Incentives promoting renewable energy production, energy efficiency and conservation, and alternative technology vehicles address both environmental and energy security concerns. Tax incentives for the domestic production of fossil fuels also promote energy security by attempting to reduce the nation's reliance on imported energy sources. The idea of applying tax policy instruments to energy markets is not new. Until the 1970s, however, energy tax policy had been little used, except to promote domestic fossil fuel production. Recurrent energy-related problems since the 1970s—oil embargoes, oil price and supply shocks, wide petroleum price variations and price spikes, large geographical price disparities, tight energy supplies, and rising oil import dependence, as well as increased concern for the environment—have caused policymakers to look toward energy taxes and subsidies with greater frequency. The direction of U.S. energy tax policy has changed several times since the 1970s. During the 114 th Congress, energy tax policy appears to be designed to encourage energy efficiency and renewable energy production while continuing to promote U.S. energy security. Several expired energy tax incentives were extended through 2016 as part of the Consolidated Appropriations Act, 2016 ( P.L. 114-113 ). Tax incentives for wind and solar were given longer-term extensions coupled with phaseouts. Absent further legislative action in the 114 th Congress, several energy-related tax provisions will expire at the end of 2016. The President's FY2017 budget proposed a number of changes to energy tax policy. Specifically, the Obama Administration has proposed repealing a number of existing tax incentives for fossil fuels, while providing new or expanded incentives for carbon sequestration, alternative and advanced technology vehicles, renewable electricity, energy efficiency, and advanced energy manufacturing. Similar proposals appeared in past Obama Administration budgets. The FY2017 budget also proposes imposing a per-barrel fee on oil. The economic rationale for interventions in energy markets helps inform the debate surrounding energy tax policy. This report begins by providing background on the economic rationale for energy market interventions, highlighting various market failures. After identifying possible market failures in the production and consumption of energy, possible interventions are discussed. The report concludes with an analysis of the current status of energy tax policy. The Appendix of this report provides a brief summary of energy tax legislation from the 108 th through 113 th Congresses that has shaped current energy tax policy. The primary goal of taxes in the U.S. economy is to raise revenues. There are times, however, when tax policy can be used to achieve other goals. These include the use of tax policy as an economic stimulus or to achieve social objectives. Tax policy can also be used to correct for market failures (for example, the under- or over-supply of a good), which without intervention result in market inefficiencies. There are a number of market failures surrounding the production and consumption of energy. Tax policy, as it relates to energy, can be used to address these market failures. There are a variety of circumstances in which government intervention in energy markets may improve market outcomes. Generally, government intervention has the potential to improve market outcomes when there are likely to be market failures. Externalities represent one of the most important market failures in energy's production and consumption. Market failures in energy markets also arise from principal-agent problems and information failures. Concerns regarding national security are used as a rationale for intervention in energy markets as well. An externality is a spillover from an economic transaction to a third party, one not directly involved in the transaction itself. Externalities are often present in energy markets as both the production and consumption of energy often involve external costs (or benefits) not taken into account by those involved in the energy-related transaction. Instead, these externalities are imposed on an unaffiliated third party. The market mechanism will likely lead to an economically inefficient level of production or consumption when externalities are present. When externalities are present, markets fail to establish energy prices equal to the full cost to society of supplying the good. The result is a system where price signals are inaccurate, such that the socially optimal level of output, or allocative efficiency, is not achieved. Economic theory suggests that a tax be imposed on activities associated with external costs, while activities associated with external benefits be subsidized—in order to equate the social and private marginal costs. These taxes or subsidies are intended to provide a more efficient allocation of resources. Many energy production and consumption activities result in negative externalities, perhaps the most recognized being environmental damage. Air pollution results from mining activities as well as from the transportation, refining, and industrial and consumer use of oil, gas, and coal. Industrial activity can also produce effluents that contaminate water supplies and lead to other damages to the land. These environmental damages can lead to lung damage and a variety of other health problems. The use of fossil fuels, both in the production of energy (e.g., coal-fired power plants) and at the consumer level (e.g., using gasoline to power automobiles), and the associated greenhouse gas emissions are widely claimed to have contributed to global climate change. There may also be market failures associated with external benefits stemming from the process of learning-by-doing. Learning-by-doing refers to the tendency for production costs to decline with experience. As firms become more experienced in the manufacturing and use of energy-efficient technologies their knowledge may spill over to other firms without compensation. In energy markets, early adopters of energy-efficient technologies and practices may not be fully compensated for the value of the knowledge they generate. Market failures in energy use may also arise due to the principal-agent problem. Generally, the principal-agent problem exists when one party, the agent, undertakes activities on the behalf of another party, the principal. When the incentives of the agent differ from those of the principal, the agent's activities are not undertaken in a way that is consistent with the principal's best interest. The result is an inefficient outcome. In energy markets, the principal-agent problem commonly arises when one party is responsible for making equipment purchasing choices while another party is responsible for paying the energy costs, which are related to the efficiency level of the purchased equipment. For residential rental properties, the incentives for the landlords and tenants surrounding the adoption of energy-savings practices are often not aligned, demonstrating the principal-agent problem. Landlords will tend to under-invest in energy-saving technologies for rental housing when the benefits from such investments accrue to tenants (i.e., tenants are responsible for paying their own utilities) and the landlord does not believe the costs of installing energy-saving devices can be recouped via higher rents. Tenants do not have an incentive to invest in energy-savings technologies in rental units when their expected tenure in a specific property is relatively short, and they will not have enough time to reap the full benefits of the energy-conserving investments. There is also evidence that when utilities are included in the rent, tenants do not engage in energy-conserving behaviors. On the other hand, when tenants pay utilities on their own, energy-saving practices are more frequently adopted. The implication is that inefficient energy use by tenants in apartments where utilities are included as part of the rent would offset energy-saving investments made by landlords; consequently, landlords under-invest in energy efficiency. In general, the under-investment in energy conservation measures in rental housing provides economic rationale for intervention. In another example, the incentives of homebuilders and homebuyers may not be aligned. Consequently, the principal-agent problem may result in an inefficient utilization of energy-efficient products in newly constructed homes. Homebuilders may have an incentive to install relatively low-efficiency products to keep the cost of construction down, if they do not believe that the cost of installing energy-efficient products will be recovered upon sale of the property. The value of installing energy-efficient devices may not be recoverable, if builders are not able to effectively communicate the value of energy-efficient devices once installed. Further, since homebuilders are not able to observe the energy use level of prospective buyers they may not be able to choose the products that best match the use patterns of the ultimate energy consumer. The result may be less energy efficiency in new homes. There are also informational problems that may lead to underinvestment in energy-efficient technologies. For example, homeowners may not know the precise payback or rate of return of a specific energy-efficient device. This may explain the so-called "energy paradox"—the empirical observation that consumers require an abnormally high rate of return to undertake energy-efficiency investments. Preserving national security is another often-cited rationale for intervention in energy markets. However, in recent years, the proportion of petroleum consumed in the United States imported from foreign countries has declined. In 2015, about 24% of petroleum consumed in the United States was imported, the lowest level since 1970. There are potentially a number of external costs associated with petroleum importation, especially when imported from unstable countries and regions.