In addition to a decline in gross domestic product (GDP) in 2009 of 2.4%, the energy intensity of the economy (energy consumed per dollar of GDP) declined 2.4% and the carbon intensity of the energy supply (carbon dioxide per unit of energy consumed) declined by 2.3%. The latter two factors led to a decline in the overall carbon intensity of the economy (carbon dioxide per dollar of GDP) of more than 4.5% between 2008 and 2009.

The large decline in emissions was driven by the economic downturn, combined with an ongoing trend toward a less energy-intensive economy and a decrease in the carbon-intensity of the energy supply.

—EIA Administrator Richard Newell

Carbon intensity changes in the electric power and industrial end use sectors. Source: EIA. Click to enlarge.

In 2009, the carbon intensity of the electric power sector decreased by nearly 4.3%, primarily due to fuel switching as the price of coal rose 6.8% from 2008 to 2009 while the comparable price of natural gas fell 48% on a per Btu basis. Increased use of natural gas in place of coal caused the sector’s carbon intensity to decrease. The industrial sector, also a large coal consumer, showed a similar decline in carbon intensity in 2009—more than 3%—due to lower coal and petroleum consumption.

Since 2000, the carbon intensity of energy used in the two sectors has not decreased (or improved) by as much as 2 percent. A decline in carbon intensity of over 4 percent in the electric power sector and over 3 percent in the industrial sector in the same year is unprecedented. This drop in carbon intensity added to the general trend towards a less energy-intensive economy, resulting in the very substantial decline in carbon dioxide emissions in 2009.

—EIA

Total energy consumption fell across all end-use sectors by 4.8%, attributable to a decline in energy intensity of around 2.4%, plus a decline in GDP of 2.4%. While this drop in energy intensity was large, EIA noted, it is not unprecedented. The average decline in energy intensity from 2000 to 2008 was 2.0%.

The industrial end use sector saw the greatest drop in energy consumption—9.9%—and the largest end use sector decrease in CO₂ emissions—13.4%—due to an accompanying 3% drop in the carbon intensity of the fuels used.

Emissions by end-use sector, 2008 and 2009. Data: EIA. Click to enlarge.

Transportation. The transportation sector saw the smallest percentage decrease of any of the end use sectors: 4.1%, to 1,851 million metric tons. Residential and commercial each saw a 4.9% drop.

The transportation sector is about 95% dependent on petroleum for its energy; motor gasoline alone accounts for about 60% of total transportation energy use. In 2007, total consumption of petroleum-based fuels averaged 14,287 thousand barrels per day. In 2008 that dropped to 13,712 thousand barrels per day; by 2009 it was to 13,277 barrels per day: 7.1% lower than 2007 and 3.2% lower than 2008.

EIA ascribes the drop in demand in 2008 primarily to a spike in fuel prices during the first half of the year followed by an accelerating economic slide. In 2009 the continuing economic downturn further lowered demand despite average fuel prices that remained well below their 2008 level. The fuel economy of the total US fleet improved from 27 mpg US in 2008 to 28.5 mpg US in 2009.