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# How Much Energy Does It Take to Build a Car?

Thousands of cars are built every day. So as we move into an era of environmental awareness and energy efficiency, let's try to estimate just how much energy is used to build a car.

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?

## 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?

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.