U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
Energy-Related Carbon Dioxide Emissions at the State Level, 2000-2013
Release Date: October 26, 2015 | Next Release Date: December 2016 | full report
Energy-related carbon dioxide (CO2) emissions vary significantly across states, whether considered on an absolute (Figure 1) or per capita basis. Total state CO2 emissions include those from direct fuel use across all sectors, including residential, commercial, industrial, and transportation, as well as primary fuels consumed for electric generation. The overall size of a state, as well as the available fuels, types of businesses, climate, and population density, play a role in determining the level of both total and per capita emissions. Additionally, each state's energy system reflects circumstances specific to that state. For example, some states have abundant hydroelectric supplies, while others contain abundant coal resources. This paper presents a basic analysis of the factors that contribute to a state's CO2 profile. This analysis neither attempts to assess the effect of state policies on absolute emissions levels or on changes over time, nor does it intend to imply that certain policies would be appropriate for a particular state.The term energy-related CO2 emissions, as used in this paper, includes emissions released at the location where fossil fuels are consumed. Therefore, to the extent that fuels are used in one state to generate electricity that is consumed in another state, emissions are attributed to the former rather than the latter. Analysis attributing emissions to the consumption of electricity, rather than the production of electricity, would yield different results. For feedstock application, carbon stored in products such as plastics are subtracted from reported emissions for the states where they are produced.
Total state emission levels
Over the time period from 2000 to 2013, CO2 emissions fell in 37 states and rose in 13 states (Table 1). The greatest percentage decrease in CO2 emissions occurred in Maine at 27%, or 6 million metric tons (mt). The greatest absolute decline was 52 million mt in New York (25%). The state with both the greatest percentage and absolute increase was Nebraska, at 28% (11 million mt).
From 2012 to 2013, 16 states saw a decrease in emissions, while 34 experienced an increase. This is reflected in the national data for 2013 as emissions were up about 2.5%. Because of differences in data aggregations it is difficult to compare the total for all states with the total for the United States. See Appendix A for a comparison of levels of data detail between the state and national data systems.
Emissions by fuel
States exhibit very different emissions profiles by fuel type (Table 2). For example, in 2013, coal consumption accounted for 78% of CO2 emissions in West Virginia. In California, 1% of CO2 emissions came from coal, with 62% from petroleum. In Rhode Island, which had no emissions from coal, 47% of emissions were from natural gas. Hawaii's and Vermont’s share of CO2 emissions from petroleum in 2013 were 92% and 91%, respectively. Maine's petroleum share was 77%. No other state's petroleum share exceeded 70%.
Emissions by sector
There can also be significant variations in terms of CO2 emissions by sector (Tables 3 and 4). These variations are due to factors such as the use of different fuels for electricity generation, climate, and sources of economic outputs (e.g., commercial versus industrial activity). For example, in Vermont the largest share of emissions in 2013 came from the transportation sector (56%), predominantly from petroleum, but the electric power sector share was 0.2% because Vermont had almost no generation using fossil fuels. Vermont's residential sector share was 23%—indicative of a relatively cold climate where petroleum is the main heating fuel. Hawaii, where a dominant share of emissions is also from petroleum, had a residential share of 0.3%—the lowest in the United States, because of minimal heating fuel requirements. The largest sector emissions share in Hawaii, like Vermont, was from the transportation sector (53%). However, unlike Vermont, Hawaii's electric power sector share was relatively high (37%). The dominant fossil fuel for the generation of electricity in Hawaii is petroleum.
Per capita carbon dioxide emissions
Another useful way to compare total CO2 emissions across states is to divide them by state population and examine them on a per capita basis (Table 5 and Figure 2). Many factors contribute to variation in the amount of emissions per capita, including climate, the structure of the state economy, population density, energy sources, building standards and explicit state policies to reduce emissions. The 2013 CO2 emissions in Wyoming were 117 mt per capita, the highest in the United States. In 2013, Wyoming was the second- largest energy producer in the United States. Unlike the largest energy producer, Texas, with a population of 26 million, Wyoming has less than 600,000 people, giving Wyoming the lowest population density in the lower 48 states.1 Its winters are cold (the average low temperatures in January range between 5 to 10 degrees Fahrenheit2). These factors act to raise Wyoming's per capita emissions compared to other states. The second-highest state per capita CO2 emissions level was North Dakota at 78 mt per capita. West Virginia (50 mt per capita), Alaska (49 mt per capita), and Louisiana (42 mt per capita) round out the top five states in terms of per capita CO2 emissions.
New York, with a population of 19.6 million people, had the lowest per capita CO2 emissions – 8 mt per capita. A large portion of the population is located in the New York City metropolitan area where mass transit is readily available and most residences are multi-family units that provide efficiencies of scale in terms of energy for heating and cooling. The New York economy is oriented towards low-energy-consuming activities such as financial markets. For example, New York contained about 6% of the U.S. population in 2013, but consumed only 1% of the country’s industrial energy.3New York's energy prices are relatively high (the average retail electricity price of 15.20 cents per kWh was fourth highest in the country in 2013), which in turn encourages energy savings.4 The other states with lowest per capita CO2 emissions—all around 9 mt per capita—include California, Connecticut, Rhode Island, and Vermont.
The energy intensity of a state, as measured by the amount of energy consumed per unit of economic output or, specifically, British thermal units (Btu) per dollar of a state's gross domestic product (GDP), plays an important role in its overall emissions profile (Table 6). The states with the highest rates of emissions per capita in 2013 also tended to have the higher energy intensity values: Wyoming (25,000 Btu per chained 2009 dollar of GDP), Louisiana, North Dakota, and West Virginia (all around 18,000 Btu per dollar), and Montana (14,000 Btu per dollar). California, Connecticut, Maryland, Massachusetts, New York, and Rhode Island were the lowest – all around 3,000 Btu per dollar or less. Many of the states with the lowest energy intensity are clustered in the relatively densely populated New England and Middle Atlantic regions. The 2013 national average was 6,000 Btu per dollar of GDP.
Carbon intensity of the energy supply
The carbon intensity of energy supply (CO2/Btu) is reflective of the energy fuel mix within a state (Table 7). As with energy intensity, the states with high carbon intensity of energy supply tend to be the states with high per capita emissions. The top five states in 2013 in terms of the carbon intensity of the energy supply as measured in kilograms of CO2 per million Btu (kg CO2/MMBtu)—West Virginia (80 kg CO2/MMBtu), Wyoming (77 kg CO2/MMBtu), Kentucky (76 kg CO2/MMBtu), Utah (72 kg CO2/MMBtu), and North Dakota (71 kg CO2/MMBtu)—are all states with coal as the dominant emissions source (Table 2). The national average carbon intensity of the energy supply in 2013 was 55 kg CO2/MMBtu. The states with lower carbon intensity of their energy supply tend to be those states with relatively substantial non-carbon electricity generation such as nuclear or hydropower. These states include, for example, Vermont (26 kg CO2/MMBtu), Washington (35 kg CO2/MMBtu), Oregon and New Hampshire (both 36 kg CO2/MMBtu), and Maine (38 kg CO2/MMBtu).
Carbon intensity of the economy
Another measure, the overall carbon intensity of the economy (CO2/dollar of state GDP), combines energy intensity with the carbon intensity of that state's energy supply. As one would expect, the states with the highest carbon intensity of their economies (Table 8) as measured in metric tons (mt) of CO2 per million dollars of state GDP (mt CO2/million chained 2009 dollars of GDP) are also the states with the highest values of energy intensity and carbon intensity of that energy supply. In 2013, these states included: Wyoming (1,915 mt CO2/million dollars of GDP), West Virginia (1,441 mt CO2/million dollars of GDP) North Dakota (1,247 mt CO2/million dollars of GDP), Louisiana (918 mt CO2/million dollars of GDP), and Montana (819 mt CO2/million dollars of GDP). The 2013 U.S. average was 336 mt CO2/ million dollars of GDP. The states with the lowest carbon intensity of economic activity are also states that appear on the lower end of both energy intensity and the carbon intensity of that energy supply. These states include: New York (128 mt CO2/million dollars of GDP), Connecticut (148 mt CO2/million dollars of GDP), Massachusetts (157 mt CO2/million dollars of GDP), California (172 mt CO2/million dollars of GDP) and Maryland (182 mt CO2/million dollars of GDP).
This analysis assigns all emissions related to the primary energy consumed for the production of electricity to the state where that electricity is produced rather than where it is consumed. As a result, the states that produce electricity from fossil fuels (especially coal) and sell that electricity across state lines tend to have higher per capita CO2 emissions than states that consume more electricity than they produce (Table 9). If the emissions associated with the generation of electricity were allocated to the states where that electricity is consumed, in many cases, the emissions profiles of both the producing and consuming states would be different.
Historically, the primary non-carbon-producing energy forms have been nuclear and hydroelectric generation. Neither energy form has experienced significant capacity increases in the United States in recent years. On the other hand, non-hydropower renewable energy forms such as wind have experienced significant growth over the past decade. While California dominated wind generation in 2000 (Figure 3), the northern and southern plains have seen the fastest growth in recent years. In 2005, Texas and California generated about the same amount from wind, but in 2013 Texas generated almost three times the amount of electricity from wind as California, which has fallen to third behind Iowa. The concentration of wind generation is also spreading beyond the initial states. In 2000, the top four states accounted for 93% of wind generation, but by 2013, even with the addition of Oklahoma and Illinois, the share of those six states had fallen to 56%. Oklahoma, which had no wind generation in 2002, was rapidly approaching California in wind generation by 2013. If Texas had generated the same amount of energy from a roughly equal mix of coal and natural gas as it did from wind in 2013, it would have produced about 22 million mt more in CO2 emissions, slightly more than Vermont's and New Hampshire's total emissions in 2013 combined. Other states are adding more solar from both utility-scale power stations, as well as distributed generation, to their energy mix. In 2013, California produced about 36% of the U.S. total of 305 trillion Btu and was the only state to produce significant energy from both wind and solar. Other leading solar energy states included Florida (16% of U.S. total), Arizona (12%), and New Jersey (8%).
See Appendix B for other EIA state-related energy and environmental products.
1U.S. Energy Information Administration, State Profiles and Energy Estimates: http://www.eia.gov/state/.
4U.S. Energy Information Administration, State Electricity Profiles, Table 1, 2013 Summary Statistics http://www.eia.gov/electricity/state/newyork/pdf/New_York.pdf.
See carbon dioxide emissions by state