U.S.-China Race to Zero Emissions (R2ZE) Challenge Infographic 
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The infographic depicts the U.S. Bus Vehicle and Commuter Bus Vehicle Power Sources continuing to climb over the past decade. In 2005, 1.1% of all buses were powered from an electric/other energy source. In 2010, 7% of buses were power by electricity. More recent numbers from 2014 show that nearly 18% of all buses in the U.S. run off of electric/other energy sources. 

Regarding the total number of electric and hybrid buses deployed in the U.S., Figure 1 offers a visual representation per every one thousand buses. In 2007 1,501 electric and hybrid buses were operating in the U.S. That number increased to 4,637 in 2010, and was measured at 8,705 in 2014. 

Meanwhile, the overall price of electric buses has decreased. Figure 1 graphically depicts the cost of electric buses per $400,000. In 2010, the average cost of an electric bus was $1,000,000. The 2015 average cost per electric bus had dropped to $800,000. 

Cost per kilowatt hour for electric batteries in buses is presented in Figure 1 in $500 increments. In 2008, the cost per kilowatt hour was $1,000. By 2013 a substantial decrease to a cost of $325 per kilowatt hour was observed. 

While cost for electric batteries deceased, battery density increased. Figure 1 measures battery density in units of 50 watt-hours per liter. In 2008, density of electric batteries in buses averaged 60 watt-hours per liter. Averaged again in 2013, the battery density had increased to 150 watt-hours per liter. 

Fuel Economy of Buses 

In Figure 2, average fuel economy is compared between diesel, compressed natural gas, fuel cell, and battery electric buses, with diesel serving as the benchmark.  In comparing compressed natural gas buses to traditional diesel buses, compressed natural gas averages 4.5 miles per gallon equivalent. The difference is far greater when comparing diesel to battery electric and fuel cell buses. Fuel cell buses achieve a greater fuel economy at 7.3 miles per gallon equivalent compared to a diesel bus. Battery electric buses enjoy the greatest fuel economy, traveling 17 miles per diesel gallon equivalent.

Annual Tailpipe Emissions

Data in Figure 3 compare major tailpipe emissions and fuel costs between diesel, compressed natural gas, fuel cell, and battery electric buses. Fuel costs are accurate as of July 2015. Figure 3 reports tailpipe emissions  resulting from carbon dioxide, nitrous oxide, hydrocarbons, and particulate matter per bus annually.

Fuel and Maintenance Costs

• Annual tailpipe emissions from buses burning diesel as a source of energy include 2,417 (g/mi) of carbon dioxide, 2.04 (g/mi) of nitrous oxide, .028 (g/mi) of hydrocarbons, and .014 (g/mi) particulate matter. The average cost of diesel per gallon in July 2015 was $2.63, resulting in an average annual fuel cost of $9,075.
• Annual tailpipe emissions from buses burning compressed natural gas as a source of energy include 2,305 (g/mi) of carbon dioxide, .65 (g/mi) of nitrous oxide, 3.12 (g/mi) of hydrocarbons, and .001 (g/mi) particulate matter. The average cost of compressed natural gas per gallon in July 2015 was $2.12, resulting in an average annual fuel cost of $4,750. 
• Annual tailpipe emissions from hydrogen fuel cells as a source of energy include 0 (g/mi) of carbon dioxide, 0 (g/mi) of nitrous oxide, 0 (g/mi) of hydrocarbons, and 0 (g/mi) particulate matter. The average per gallon equivalent cost of hydrogen fuel cells in July 2015 was $4.50, resulting in an average annual fuel cost of $3,250.
• Annual tailpipe emissions from buses using electricity as a source of energy include 0 (g/mi) of carbon dioxide, 0 (g/mi) of nitrous oxide, 0 (g/mi) of hydrocarbons, and 0 (g/mi) particulate matter. The average per gallon equivalent cost of electricity in July 2015 was $1.29, resulting in an average annual fuel cost of $1,770.