Gas or Electric? Thinking Algebraically About Car Costs, Emissions and Trade-offs
Dashiell Young-Saver, New York Times Learning Network
This is an activity that uses basic algebra to assess the costs and savings of electric vehicles. It uses math to measure the trade-offs of buying electric versus gas-powered car models.
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Provide students with the student PDF link ([link https://int.nyt.com/data/documenttools/thinking-algebraically-about-car-costs-emissions-and-trade-offs-student-version/4d500c9febb5fcf0/full.pdf]) rather than the NYTimes webpage link. Note that the interactive graphs are missing. The activity will still work even if the article it is based on is inaccessible or outdated.
Consider breaking the activity into two daysâday 1 for warm-up questions and required reading, and day 2 for math activities.
Consider incorporating more choices in lessons such as by letting students choose their own cars to compare.
If the carbon counter tool is updated, the lesson should age ok and may hold timeliness more for upper middle school than high school. The EPA also has a tool ([link epa.gov/energy/greenhouse-gas-equivalences-calculator]) so a comparison of the two calculators with the same cars could be added.
The premise is straightforward and related to real-world considerations. This might be something students would like to take home with them to contribute to a family decision, or to make an argument for their first car.
This resource is designed to get students thinking about the financial costs and greenhouse gas emissions of electric vs. gas cars.
The math used is pretty straightforward algebra. The data is provided along with links to tools for identifying and modeling variables involved in the calculations.
The lesson flow is logical, and the data is clearly shown in tables. There are numerous links to other sources of information which add confidence to the data.
Several concepts related to electric vehicles are overlooked and teachers may want to address these issues when teaching. For example, there is minimal discussion of electric vehicle batteries and the cost of replacing them or environmental concerns of creating them (although this may be considered in the lifetime cost of the electric vehicle). It also does not address the electric vehicle range and lack of fueling stations, although this challenge is improving for electric vehicles.
There is mention of extending the activity to look at hybrid vehicles but hybrid and diesel vehicles aren't the focus, only light-duty gas and electric vehicles are specifically analyzed.
The instructor may want to introduce the concept of heavy-duty versus light-duty and the different vehicle fuel standards (cars vs. trucks).
Comments from expert scientist:
This resource is great for using a relatable example (i.e. car choice) to teach the complexities of sustainable decision making (tradeoffs between cost and environmental impact). This resource encourages student's to think of sustainability in a broader context then simply tailpipe car emissions by considering lifetime costs and emissions. My only concern is that this exercise simplifies a very complex discussion. The answer to "which is better environmentally" is often dependent on the assumptions made and how "better environmentally" is defined. Because of this, when comparing life cycle emissions it is important to clearly state assumptions. For example, the fuel source for electricity generation can be decisive in the overall emissions of electric cars (i.e., if coal is used to generate electricity an electric car can have worse life cycle CO2 eq. emissions compared to a conventional gasoline car). I think it would be valuable to include a question for students to reflect on the assumptions that were made in these analyses. For example, in the second half of the exercise it may be valuable to include a question along the lines of "If the electric car's electricity was generated using a coal power plant the emissions associated with charging the battery would increase to XXX - How does this shift the breakeven point for when the Camry would produce more emissions than the Tesla?" This carbon counter website referenced in this resource uses data from a 2016 publication, which may become outdated in the coming years as more and more electric car options become available.
This activity is pretty straightforward in terms of the data and calculations. It is also very complete and follows logical steps to identify and model different variables. The sequence of questions guiding students through the calculation is well designed to make the exploration real and convincing.
Some math and graph-reading skills are needed. A student worksheet is provided that does not have answers. The NYTimes website page has answers and is not formatted well for students.
This is a good lesson for students to work through individually or in groups.
The activity scaffolds very well. It introduces the topic slowly but ends with resources and suggestions for further inquiry.
The student worksheet clearly steps students through the activity with links and resources. Minimal teacher input is required.
The NYTimes website page has distracting advertising and shows the answers to the activity. It is recommended that teachers provide students with the student PDF instead of the NYTimes webpage.
A school must have access to NYTimes for the lesson (freely provided to schools), but a PDF version is available for download. The instructor may also want to download the required reading NYTimes article about electric vs gas vehicles in advance and provide PDFs to the students.
