The Worldwide Energy Budget

Examining worldwide energy use is important for two related reasons. First, one of the most thorny issues in setting a course toward sustainable energy is the problem of which countries should bear the cost of shifting their energy use. Currently, developed countries use far more energy per capita than developing countries do, and developing countries are understandably reluctant to inhibit their economic growth by agreeing to any restrictions in how they generate energy. At the same time, the magnitude of the problem we are facing with our energy supply can only be understood by asking the question, "What if developing countries do manage to bring themselves up to the level of the developed ones?" Therefore, the second reason for looking at worldwide energy use is that it provides rough guidance about what demand might look like in the future.

Table 1 quantifies the amount of energy consumed and the amount of greenhouse gases emitted by the five largest economies in 2005. The total for all countries is listed at the bottom of the table. One can see that these five countries make up 55% of the worlds gross domestic product (GDP), 47% of its energy use, and 47% of its greenhouse gas emission, but only 29% of the world's population. These numbers suggest that by considering only a handful of countries, we might be able to get a pretty good idea of how energy is used worldwide.
Table 1: Total Energy Consumption for the Five Largest Economies (2005)
Country GDP Population Energy Use Greenhouse Gases
(trillions USD) (millions) (billion MWh) (billion tons CO2 equiv.)
United States 12.4 296 29.5 7.0
Japan 4.5 128 6.7 1.3
Germany 2.8 82 4.3 1.0
China 2.2 1,306 19.6 7.2
United Kingdom 2.2 60 2.9 0.6
World Total 44.2 6,476 135.4 36.5

However, if you ignore China for a moment in the list of the top five economies, the situation appears even more skewed. The U.S., Japan, Germany, and the U.K.make up only 9% of the world's population, but account for 50% of GDP, 32% of energy use, and 27% of greenhouse gas emission. China, of course, is a developing country, whose economy is so large in part because it is so populous. Therefore, to produce a more fair comparison, one can compare the amount of GDP, energy, and greenhouses gas emission on a per person basis. Table 2 does this.
Table 2: Per Capita Energy Consumption for the Five Largest Economies (2005)
Country GDP Energy Use Greenhouse Gases
(thousands USD) (MWh) (tons CO2 equiv.)
United States 42.0 99.7 23.6
Japan 35.6 52.3 10.5
Germany 33.9 51.6 11.9
China 1.7 15.0 5.5
United Kingdom 36.4 48.1 10.6
World Average 6.8 20.9 5.6

One can see that the per capita energy use in the U.S. is twice as high as in Japan, Germany, and the U.K., and over six times larger than in China. Similarly, the per capita greenhouse gas emissions in the U.S. are twice as high as in the three other wealthy nations, although it is only about four to five times higher than in China. Interestingly, China's energy use and greenhouse gas emission are more-or-less in line with the world average, although its GDP is considerably lower than the average (more on that here).

This can give us guidance as to the magnitude of the energy challenge we might be facing in the future. It seems reasonable to expect that most countries (with a few exceptions) desire a lifestyle that is at least on par with those of developed countries like Japan, Germany, the U.K., and the U.S. As it now stands, those "wealthy" lifestyles require 2--4 times more energy than the average lifestyle on Earth. So one unavoidable question is, even without considering population growth (The U.S. Census Bureau predicts the world population will grow to 9 billion by 2040, which represents an average annual growth rate of about 1%. For comparison, China's economic growth rate is about 9%, which, if this astounding growth can be maintained, would set it on a course to grow by a factor of 24 to match the 2005 U.S. GDP by 2042.), how can we accommodate future energy demands that might increase by more than a factor of 2?

Even more difficult is to imagine how we would control greenhouse gas emissions. The U.N. Human Development Report suggests that our goal should be to reduce the chance that the global climate will warm by 2 degrees Celsius in the 21st century to less than about 50%. According to their models, doing this would require that the global budget for greenhouse gases be around 14.5 billion tons of carbon dioxide equivalent per year by 2050. Per person, this is an allotment of 2.2 tons equivalent to carbon dioxide per year. This less than half the current worldwide average, and ten times lower than the per capita greenhouse gas emissions in the U.S. Under this standard, even China would have to cut its greenhouse gas emissions in half.

So, how could we possibly reduce our greenhouse gas emission that much? There are only two tools (excluding those that involve a zombie plague or an asteroid hitting the Earth): conservation, and alternative energy such as nuclear, renewable energy, or fusion. We believe that it will benefit the U.S. to tackle the energy challenge through both means. Like it or not, the developing world looks to us as a model for their economies and lifestyles. We have the resources to develop technologies, and, if necessary, to change our way of life, so that we can export that to other countries. This could be a boon to our country, if we take the lead in developing technologies such as safe nuclear power, renewable energy, and a next-generation electrical grid.

On the other hand, if we do nothing to secure our energy future, we will find ourselves importing ways of dealing with cities that lie below sea level, in an uneven exchange for exporting more of our troops on missions to deal with troubled oil-rich countries, and aid to help millions of people displaced by floods or droughts.


The values for the table were compiled from four sources. The population numbers are from the US Census Bureau International Database. The GDP numbers are originally from the CIA World Factbook, but to get the year that I wanted, I went to Nation Master. The energy use numbers are from the international section of the Energy Information Administration. Finally, the greenhouse gas numbers are from the Climate Analysis Indicators Tool, version 6. I used 2005, because that was the most recent year that the greenhouse gas numbers were available for.

While doing this analysis, I checked my work against David MacKay's book, Sustainable Energy - without the hot air, which I originally found thanks to a post by Cory Doctorow on BoingBoing.

Michael Muno: mtspaceblog at gmail
Last modified: Sun Jul 5 07:24:09 EDT 2009