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In 2018, the number of cars produced in a year peaked at 97 million. That number has since gone down due to countless shortages and high new car prices, but the point is the world builds a lot of cars. However, the ongoing debate on how clean electric cars really are to build begs a fairly simple question: how much energy goes into building a car?

Toyota Tacoma trucks on assembly like at Toyota Motor Manufacturing, Texas plant
Toyota Motor Manufacturing | Toyota

Understanding how to measure energy

In order to answer the question, I have to throw down some science-lingo. The most common unit of energy is what’s called a Joule. This is, essentially, one watt of power being used for one second. A Megajoule, or MJ, is a million Joules, and a Gigajoule, or GJ, is a billion Joules.

This unit can be used for many sources of energy, from coal-powered to wind-powered, and even gasoline. The production of a car is typically measured in gallons of gas, which makes things fairly easy for our automotive brains to understand. A gallon of gas is about 120 MJ, or 120 million Joules, which is a highly dense amount of potential energy.

With that very basic understanding of how energy is measured, let’s translate that to cars. Specifically, how much energy, on average, goes into building one.

How much energy goes into building an average car?

Robotic Arms Assembling GM Cars
Robotic Arms Assembling GM Cars | VCG/VCG via Getty Images

I’ll start by saying this is paper napkin math backed by science and research from the Multidisciplinary Digital Publishing Institute. On page 15 of the document, there’s a table that showcases the collection of three studies and their calculations on how many Megajoules per kilogram go into a car.

The formulas used by MDPI the energy used equals 41.8 MJ/kg (kgs being how many kilograms the car weighs). However, studies from the Scientific and Technical Research Reports institution of Belgium and the Center of Environmental Systems Research in Kassel, Germany have higher estimates. The first estimates that the amount of energy used is 53 MJ/kg, and the second estimates its 81 MJ/kg.

Those numbers are accurate, and for the sake of this article, we’ll be going with the 41.8 MJ/kg estimate calculated in the research paper. But this is where rough estimates come in. The average car weighs around 3,000lbs, so by converting lbs to kgs, then multiplying that by the number of Megajoules per kilogram, you have how much energy it takes to build a car.

By those estimates, you’re looking at 56,880 MJs to build a single car. In simple terms, that’s 474 gallons of gasoline. And electric cars are often considered dirtier to build, even though the zero-emissions power source counteracts that. After all, if we assume the average car has a 15-gallon gas tank, then it only takes 31 fill-ups to build another car.

Burning 31 tanks of gas to build a single car using optimistic estimates doesn’t sound clean, and that doesn’t include how many cars are built in a day. That’s why I want to pose one more hypothetical that could help clean up our future.

How much green energy would it take to build a single car?

A wind farm in rural France utilizing renewable energy.
A wind turbine farm | AFP Photo/Jean-Francois Monier/Getty Images

Where Do Charging Stations Get Their Power?

I’m talking wind, solar, and even hydropower sources that produce zero emissions and still generate energy. Now, there are a couple of calculations to make, since you don’t measure the electricity generated with Joules. A kilowatt hour, or kWh, is how many kilowatts are generated in an hour. And because a Joule is one watt in use for one second, a kWh is equal to about 3.6 MJs

So let’s start with solar panels: a single solar panel produces about 1.24 kWh per day. And in order to build a car, you’d need about 15,800 kWh of energy (56,880 MJs divided by 3.6 MJ/kWh). That adds up to 12,741 solar panels. And assuming a solar panel is 5.4 feet by 3.25 feet according to SunPower, that’s 223,620 square feet. That adds up to about five acres of land needed to build a single car per day.

Then there are wind turbines, which create around 15,000 kWh per day on average (depending on location. The closer to the ocean, the windier it is). Packing a heftier punch, you’d only need about one wind turbine to build a car in a day. And considering you can fit around 200 to 400 turbines on a five-acre plot of land (20 to 40 per acre), that’s far more efficient than solar panels.

But the strongest source of clean energy comes from hydropower. Reclamation is a collection of 58 hydropower plants in the Western United States, producing 42 billion kWh per year, or about 1.1 million kWh per day. With that amount of power going toward a car factory, you could produce 73 cars per day. However, that’s a fairly low number in the grand scheme of things.

The conclusion for this little case study

In 2020, Ford and Toyota sold over two million cars each, meaning they’d have to make almost 6,000 cars per day. And 2020 was considered a slow year in terms of new car purchases. The only power sources that can meet the amount of production needed are fossil fuels and coal. So for the foreseeable future, cars will always be built by dirty means, even if the vehicles produced are clean.