Hybrid and Plug-In Electric Vehicle Emissions Data Sources and Assumptions

The following sources and assumptions were used to calculate the emissions, fuel use, and electricity sources for conventional and electric drive vehicles on the hybrid and plug-in electric vehicle emissions page.

Electricity Sources and Annual Vehicle Emissions

The following sources and assumptions were used to show electricity sources and calculate the annual vehicle emissions for a conventional, hybrid electric, plug-in hybrid electric, or all-electric vehicle.

Parameter	Value	Source
Gasoline GHG/gal	24	Derived using GREET model version 1.8d available at http://greet.es.anl.gov
National Average Electricity GHG/kWh	1.58	Derived using GREET model version 1.8d available at http://greet.es.anl.gov
Electricity Prices		Electricity prices from http://www.ventyx.com
Electricity Fuel Mix		Mix of fuels derived for the entered zip code by disaggregating EGRID2007 data available at http://www.epa.gov/cleanenergy/energy-resources/egrid/index.html
National Average Electricity Cost $/kWh	$0.11	EIA 2011 Annual Energy Outlook, Table A3, year 2011, Residential, Nominal dollars source: http://www.eia.gov/forecasts/aeo/?src=email
Conventional Vehicle mpg	27.6	CAFÉ Standard
HEV mpg	42	Sales weighted average: 2010 sales from spreadsheet "HEV Sales by Model" (http://www.afdc.energy.gov/data/vehicles.html); MPGs from 2010 Fuel Economy Guide (http://www.fueleconomy.gov/feg/FEG2010.pdf)
PHEV mpg	37	Based on Chevy Volt specification
PHEV kWh/mi	0.36	Based on Chevy Volt specification
PHEV all-electric range	35	Based on Chevy Volt specification
EV kWh/mi	0.34	Based on Nissan Leaf specification
Average annual new car mileage (miles)	15,000	Transportation Energy Data Book 28, Table 3.7
Percentage of PHEV annual miles driven on electricity	70%	Rough average based on data from 2001 National Household Travel Survey, Summary of Travel Trends, Table 29. Assuming that the vehicle owner plugs in at home every night he/she is home and that the PHEV all-electric range is 35 miles.

Emissions and Fuel Cost for a 100-Mile Trip

The following sources and assumptions were used to calculate the emissions and fuel costs for a 100-mile trip using a conventional, hybrid electric (HEV), plug-in hybrid electric (PHEV), or all-electric (EV) vehicle.

Parameter	Value	Source
Trip Length miles	100	Given
Gasoline GHG/gal	24	Derived using GREET model version 1.8d available at http://greet.es.anl.gov
National Average Electricity GHG/kWh	1.58	Derived using GREET model version 1.8d available at http://greet.es.anl.gov
Electricity Prices		Electricity prices from http://www.ventyx.com
Electricity Fuel Mix		Mix of fuels derived for the entered zip code by disaggregating EGRID2007 data available at http://www.epa.gov/cleanenergy/energy-resources/egrid/index.html
Gasoline Cost $/gallon (national average for regular gasoline)	$3.69	http://www.aaa.com on 7/29/2011
National Average Electricity Cost $/kWh	$0.11	EIA 2011 Annual Energy Outlook, Table A3, year 2011, Residential, Nominal dollars source: http://www.eia.gov/forecasts/aeo/?src=email
Conventional Vehicle mpg	27.6	CAFÉ standard
HEV mpg	42	Sales weighted average: 2010 sales from spreadsheet "HEV Sales by Model" (http://www.afdc.energy.gov/data/vehicles.html); MPGs from 2010 Fuel Economy Guide (http://www.fueleconomy.gov/feg/FEG2010.pdf)
PHEV mpg	37	Based on Chevy Volt specification
PHEV kWh/mi	0.36	Based on Chevy Volt specification
PHEV All-Electric Range	35	Based on Chevy Volt specification
EV kWh/mi	0.34	Based on Nissan Leaf specification

Hybrid Electric Vehicle Emissions

To calculate HEV emissions, consider that during a typical 100-mile trip, an HEV averages 42 miles per gallon and uses about 2.4 gallons of gasoline. Gasoline contains about 24 pounds of CO₂ equivalent per gallon (source: GREET), resulting in 57 pounds of CO₂ emissions for the trip. At a gasoline cost of $3.69 per gallon, the trip costs $8.78.

Plug-In Hybrid Electric Vehicle Emissions

To calculate PHEV emissions, consider the emissions of both power sources: electricity from the grid and the fuel, such as gasoline.

• Electricity (first 35 miles)—The electricity used depends on the vehicle's electricity consumption while in electric mode. If the vehicle uses 360 watt-hours to travel 1 mile, the vehicle will use 12,600 watt-hours—or 12.6 kilowatt-hours (kWh)—during the first 35 miles. The amount of emissions caused by generating 12.6 kWh of electricity depends on how that electricity was generated. Using the U.S. national average grid mix (source: GREET), 12.6 kWh of electricity results in 20 pounds of CO₂. If the vehicle is charged from a non-polluting, renewable source, such as wind or solar, the emissions for this portion are zero. If electricity costs $0.11 per kWh (national average), this portion costs $1.39.

• Gasoline (remaining 65 miles)—The amount of gasoline used depends on the vehicle's fuel consumption while using the gasoline engine. If the vehicle gets 37 miles per gallon, 65 miles requires about 1.8 gallons of gasoline. Gasoline contains about 24 pounds of CO₂ equivalent per gallon (source: GREET), resulting in 42 pounds of CO₂ for this portion. At a gasoline cost of $3.69 per gallon, this portion costs $5.71.

During a typical 100-mile trip, plug-in hybrid electric vehicles with a 35-mile all-electric range that starts with a full battery charge will use electricity for the first 35 miles before switching to gasoline.

All-Electric Vehicle Emissions

To calculate EV emissions, consider the electricity consumption (in watt-hours per mile) and the fuel used to produce the electricity. EVs produce no tailpipe emissions because the electricity consumed to drive the electric motor produces no emissions. However, producing the electricity that charges the vehicle's battery might produce emissions.

During a typical 100-mile trip, EVs with an electricity consumption of 340 watt-hours per mile require 34,000 watt-hours (34 kWh) of electricity. Using the U.S. national average grid mix (source: GREET), 34 kWh of electricity results in 54 pounds of CO₂ equivalent. If the electricity used to charge an all-electric vehicle comes from a non-polluting, renewable source, such as wind or solar, driving the vehicle produces no emissions. If electricity costs $0.11 per kWh (national average), the total electricity cost for the trip is $3.74.