The Energy Cost of Making a Car

The life cycle of a car, which is the time between the car’s assembly and the end of its useful life, draws upon dozens of industries and several energy sources to supply raw materials. The actual building of a car—stamping, body welding, assembly, and painting—uses less energy than all of the premanufacture steps. Carmakers have saved costs in body building by incorporating large amounts of aluminum since aluminum is a light metal that helps increase fuel efficiency and aluminum production demands less energy and so less money than other metals, such as steel. Calculations of the energy demand of a single car tend to consider the individual materials that go into the vehicle. According to this method, the following common car materials have varying energy requirements listed here in the order of their energy demand: wrought aluminum, copper, zinc, rubber, steel, and reinforced plastic. Wrought aluminum consists of metal made by shaping solid aluminum sheets; cast aluminum is made by pouring molten aluminum into molds.

How can wrought aluminum save energy in car manufacture if it demands more total energy to make? The answer comes from the significant recycling that the automobile industry uses. A single family car represents one of the most recycled products a person will ever buy. Aluminum holds an advantage over steel because, although it requires about 105 megajoules (MJ) of energy per pound (231 MJ/kg) to make, it costs only 24 MJ per pound (52 MJ/kg) to recycle. Steel, by contrast, requires almost as much energy to recycle (24 MJ per pound [52 MJ/kg]) as it does to make (30 per pound [66 MJ/kg]).

The total energy costs of building a vehicle depend on the size of the vehicle, number and type of components, and the current price for raw materials and labor. If carmakers design their future manufacturing plants to reduce coal as an energy source and turn to renewable sources, such as solar, wind, or water, the energy costs decline. The environmental group Green Car Congress has reported that manufacturers have been consistently cutting the energy costs of making a car; total energy costs by manufacturers in Britain have dropped by one-half since 2001. Car production nevertheless drains resources and energy even with its extensive recycling. As a reference, the bicycle advocate Bicycle Universe has estimated it takes the same amount of energy to make 100 bicycles as it does to make one car.

Experts in the automotive industry have used various techniques to calculate the energy costs of making a car, but the calculations can be difficult to verify. Among all industries, vehicle manufacturing requires much less energy than petroleum and coal products, chemicals, food, paper, and iron, steel, and other metals. Vehicle production nevertheless requires energy for making the vehicle’s raw materials—aluminum, steel, plastics, rubber, glass, fluids, forgings, textiles—and energy to run the assembly process. Accounting for all these factors, the United Nations Educational, Scientific and Cultural Organization (UNESCO) has calculated that a 1.1- ton (1 metric ton) car requires 25,600 MJ to produce—25,600 million joules. (One joule is the energy needed to lift an object weighing one Newton [0.445 pounds; 0.2 kg] 3.3 feet [1 m].) To put a single car’s manufacture in perspective, the energy to make a car is about the same as the electrical energy needed to power an average house for one year.