Reliable statistics on energy production are generally available, but accurate data on energy consumption by major industrial sectors is much harder to come by. Even more challenging is obtaining precise figures on the energy consumed during the production of specific goods. These hidden energy costs are an essential part of the environmental impact we face when owning and using products.
Calculating the implied energy in manufactured goods involves a lot of simplifications and assumptions. For example, it's not just about the steel used in cars or the microchips in computers—it's about choosing representative models and making reasonable estimates. The challenge lies in selecting values that are both practical and meaningful, while the reward is gaining a fresh perspective on how our modern world is built and sustained.
When focusing on mobile devices and cars, there's a clear reason for each choice. Mobile devices drive instant communication and access to endless information, while cars offer the freedom of movement in the physical world.
A 1.4-ton car, like the Honda Accord LX, clearly contains far more energy than a 140-gram smartphone, such as the Samsung Galaxy. However, the difference in their energy content is nowhere near 10,000 times their weight difference.
In 2015, global sales reached 1.9 billion smartphones, 60 million laptops, and over 230 million tablets. Together, these devices weighed around 550,000 tons. Assuming an average hidden energy of 250 million joules per phone, 4.5 billion joules per laptop, and 1 billion joules per tablet, the total energy required for their production was approximately 1 EJ (10^18 joules). For cars, the average energy required per unit is around 100 billion joules. With 72 million cars sold globally in 2015, the total energy needed was roughly 7 EJ. Despite the car’s weight being over 180 times that of all portable devices combined, its energy cost was only seven times higher.
This might seem surprising, but even more astonishing is the comparison of energy use over time. Smartphones typically last about two years, so the energy embedded in the devices produced annually is roughly 0.5 EJ. Cars, with a service life of at least ten years, require about 0.7 EJ of energy each year—only 40% more. Even if the initial assumption were reversed, the total would still be in the same ballpark, likely within a factor of two.
Of course, the operational energy costs differ significantly. A compact American sedan uses about 500 billion joules of gasoline over its 10-year lifespan—five times the energy embedded in its production. Meanwhile, a smartphone consumes only 4 kWh of electricity over two years, which is less than 30 megajoules. If powered by renewable sources like wind or solar, this cost is negligible compared to its embedded energy. But if it relies on coal, the ratio could rise to 8%.
Yet, without a network, a smartphone becomes nearly useless. The energy required to build and maintain the internet infrastructure is massive. In 2013, U.S. data centers consumed about 91 billion kWh of electricity—2.2% of total power generation—and planned to increase that to 3.5% by 2020. Globally, information and communication networks accounted for 5% of electricity demand in 2012 and are expected to reach 10% by 2020. So, despite their small size, smartphones have a significant impact on energy use and the environment.
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