Navigant Research Blog

Energy Consumption Falling in the Transportation Sector

Scott Shepard — May 21, 2014

Climate change has been in the news a lot lately due to recently published reports from the United Nations, the White House, NASA, and myriad other scientific institutions that have highlighted the consequences of increasing levels of CO2 in the Earth’s atmosphere.  While there are many ways to reduce per capita energy consumption, one of the greatest opportunities lies in making light duty vehicles (LDVs) more energy efficient.  In no other sector is the potential for reduction so high and the pathway to achievement so accessible.

Not all energy consumption is carbon intense, but an overwhelming majority of the energy consumed in the transportation sector, born from the burning of oil, is.  Burning a gallon of gasoline (with 10% ethanol) consumes around 112,000 BTUs of energy and emits 8,887 grams of CO2.  It’s also estimated that gasoline requires around 6 kWh (20,500 BTUs) of grid-sourced electricity to refine 1 gallon of gasoline from crude oil, and the 2010 emissions factor of the U.S. grid was estimated to be 690 grams/kWh.

The Widening Gap

Given the average fuel economy of 24.7 mpg for new LDVs in 2013, the average new car in the United States consumes 5,364 BTUs/mile, emitting roughly 527 grams of CO2/mile.  The fuel economy of 2013 models has improved from the prior year by 1.2 mpg, meaning that the average car purchased in 2013 saves 274 BTUs/mile and 27 grams of CO2/mile over 2012 models, an improvement of nearly 5%.

Navigant Research estimates that, thanks to Corporate Average Fuel Economy (CAFE) standards, the average fuel economy of a new LDV will be 52% higher in 2025 than in 2013.  This means that the average new LDV will use 1,836 fewer BTUs/mile and emit 180 fewer grams of CO2/mile than 2013 models, equaling improvements of roughly 66%.

Meanwhile, the sales-weighted average of a 2013 battery electric vehicle (BEV) had a 3.1 miles/kWh rating.  This means that 2013 BEVs consume 1,100 BTUs/mile and emit roughly 222 grams of CO2/mile, a reduction of nearly 80% in energy consumption and nearly 58% in carbon emissions from conventional 2013 cars.

These calculations do not include full lifecycle emissions and energy consumption characteristics of either the gasoline or electricity supply chain; a more comprehensive analysis would no doubt improve the returns of BEVs over conventional petroleum-powered vehicles.  Additionally, a static figure of 690 grams/kWh is used to assess grid-sourced carbon emissions.  The carbon emissions intensity of the grid varies significantly by location, as seen here, and the grid will become much cleaner over time due to increased penetrations of wind and solar in the generation portfolio – furthering the energy and emissions efficiency gap between gasoline and electricity as a fuel.

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