Classroom edition · Energy resources and air pollution

Drivetrain Lab: Gas, Hybrid, Plug-in or Electric?

Pick up to four cars and a place to drive them. The lab follows each car's greenhouse gases from the factory to the fuel pump or power plant, and shows how much each one emits per mile, per year and over its life.

Where and how you drive
Town Highway
Cars to compare
Question 1

Where does each car's CO₂ come from?

Lifecycle emissions in grams of CO₂-equivalent per mile, split into building the car (including its battery), producing and delivering its fuel or electricity, and burning that fuel in the engine or at the power plant.

Building the car and batteryProducing and delivering fuelBurning fuel (tailpipe or power plant)
Question 2

How much, and what does it use?

The best value in each row is green. Energy cost is fuel or electricity only, at home charging rates; it leaves out the price of the car, insurance and repairs.

Question 3

When does a battery pay back its carbon debt?

Batteries make plug-ins and EVs dirtier to build. Each mile driven on electricity emits less than a mile on gasoline, so the gap closes over time. Each card compares a car with .

Question 4

Does it matter where the electricity comes from?

The same car, , driven miles a year in every state. Each dot is one state's grid. The line is for comparison.

Questions to discuss
  1. In Question 1, which part of the bar is largest for the gas car? For the EV? Why is the "building" part bigger for the EV?
  2. Switch the state to West Virginia, then Washington. Why does the EV's lifecycle CO₂ change so much while the gas car's barely moves? Look up which energy sources each state's grid uses.
  3. Set the miles per year to 5,000, then 25,000. How does the payback time in Question 3 change, and why?
  4. Try a cold climate. Which drivetrain loses the most efficiency, and what causes it?
  5. A gas car pollutes at its tailpipe; an EV's pollution happens at a power plant. Who breathes the air near each source? How does that connect to environmental justice?
  6. The smog rating measures pollutants like NOₓ and particulates, not CO₂. Which drivetrain is best for local air quality, and why might a hybrid beat a gas car on both measures?
  7. Compare the hybrid with the plug-in hybrid. When would a hybrid be the lower-emission choice?
How the numbers are calculated
  • Fuel use: EPA town and highway ratings (mpg for gas and hybrids, kWh per 100 miles for EVs), blended by your town/highway slider. Hot climates add 3% to gas use and 8% to electricity use; cold climates add 8% and 20%.
  • Plug-in hybrids: the share of miles on electricity is estimated from the car's electric range and your daily miles, up to 90%. The rest are driven on gasoline.
  • Gasoline: 10,700 g CO₂e per gallon from well to wheels: 8,887 g burned at the tailpipe plus about 1,800 g for drilling, refining and transport (Argonne GREET).
  • Electricity: your state's grid emissions from EPA eGRID2023, plus 4.2% lost on power lines and 10% for producing and shipping the coal, gas or uranium the plants burn (an estimate). eGRID counts power where it is made, so states that import or export a lot of electricity can look cleaner or dirtier than what flows in their wires.
  • Building the car: 6.5 to 11 metric tons CO₂e for a gasoline car body, depending on size. Hybrids add 0.4 t. Plug-ins and EVs add 70 kg per kWh of battery; EVs subtract 2 t for the engine and transmission they don't need. This is spread over the miles a car of that size usually drives in its life: 191,000 for cars, 211,000 for SUVs, 244,000 for pickups (University of Michigan, 2025).
  • Smog rating: EPA's 1–10 window-sticker score for tailpipe pollutants that form ground-level ozone. EVs have no tailpipe and score 10.
  • Energy cost: state average regular gasoline (AAA, Oct 15, 2026) and home electricity (ElectricChoice, Oct 2026).

Sources: EPA eGRID2023 · EPA fueleconomy.gov · DOE/Argonne cradle-to-grave analysis · ICCT 2025 · AAA gas prices

Drivetrain Lab Classroom Edition from Oddly Audacious Apps. For the full cost comparison with prices, loans, leases and insurance, use Drivetrain Cost Lab for Car Shoppers. Lesson plans and student sheets: Drivetrain Lab for teachers. Numbers are estimates for teaching and comparison.