Calculations for Energy Use in Flying

Jan 11, 2012 | Air Travel

These calculations have been prepared for GHSP, Inc, in support of the PBS series

EARTH: THE OPERATORS' MANUAL

Many users of carbon calculators are surprised to find that air travel is one of their largest energy uses. It takes only a few trips to make this item one-third or more of an individual's energy use.

Again, smart defaults are used to simplify the personalization.  As the bar chart below shows, most Americans don't fly, and a few citizens travel frequently.  Flying is an area where personalization can be very helpful.



Using data from the Department of Transportation, U.S. Bureau of Transportation Statistics, we offer the user an input area to enter the number of flights taken per year by category. The summary energy and CO2 results are also shown in the following table:

The amount of energy used in flying is highly dependent on the length of the trip, so this detail is important to get a reasonable estimate of personal energy use.  Also, longer trips use more fuel per passenger mile - a second way that trip length affects energy use.

The energy use is calculated as follows:

Energy use per mile flown is 2735 Btu per passenger per mile for domestic flights and 3211 Btu per passenger miles for overseas flights.


Energy use per flight (short or medium) =

Miles flown X 2735 BTU per passenger mile 

Energy use per flight (long) =

Miles flown X 3211 BTU per passenger mile 



In the interactive web tool the user selects the number of flights made in the past year by trip length and the web tool presents the total energy use from flying.

Energy used in flying =
[# short trips X BTU per short trip ]
+ [# medium trips X BTU per medium trip ]
+ [# long trips X BTU per long trip ]

The calculations to estimate CO2e emissions are a bit more complex. EIA reports that there are 9.57 pounds of CO2 per kg of jet fuel. 2.2 kg per pound was used to convert this data to 21.054 pounds CO2 per gallon of jet fuel.


The CO2 per flight is then:
CO2 per flight (domestic) =
trip length in miles X 60.2 passenger miles per gallon of jet fuel X 21.054 pounds of CO2 per gallon of jet fuel 

CO2 per flight (international) =
trip length in miles X 52.1 passenger miles per gallon of jet fuel X 21.054 pounds of CO2 per gallon of jet fuel 

Keywords:  Energy use in flying; carbon emission from air travel; airline emissions; airline energy use.