Energy Intensity of GDP for Top Economies (2021)

Introduction

Fig. 1: Energy intensity of GDP (MJ per $) for selected countries in 2021. (Image source: N. Wang)

In this note, I compute the energy intensity of GDP (EI) for five of the world's largest economies in 2021, the United States, China, Japan, India, and Germany. EI is measured in joules per U.S. dollar (energy used per year divided by GDP per year) and serves as a quantitative indicator of how much energy a country requires to produce economic value. A lower EI indicates a more energy efficient economy, generating more GDP per unit of energy, while a higher EI reflects greater energy use for each dollar of output.

We wish to measure and compare how efficiently these leading economies convert energy into economic activity, and to explore what these differences reveal about their industrial structures, stages of development, and overall energy dependence.

Data and Methods

Primary energy for 2021 is taken from the BP Statistical Review of World Energy 2022. [1] GDP for 2021 (current US dollars) is taken from the World Bank's World Development Indicators. [2] Energy intensity is reported in MJ per US dollar: 1 EJ = 10¹⁸ J and 1 MJ = 10⁶ J, so EI = EJ × 10¹² $^-1.

Results

Discussion

The data shows that economic output is closely tied to energy use across all five countries examined. As shown in Fig. 1, China and India exhibit the highest energy intensity, while the United States and Germany achieve far greater economic output per unit of energy consumed. Table 1 summarizes the key GDP and energy data used in this analysis. Its also important to note that primary energy and GDP figures come with uncertainty, especially for countries like China and India where data reliability and reporting standards differ. The true values may therefore vary slightly from those presented here. Similar analyses have been performed by Bonnet, though this paper uses more recent data and focuses on comparative intensity across major economies. [3] Drawing off previous analyses, I argue that each nation converts physical energy into economic activity at a consistent ratio, confirming that energy consumption and GDP move together. Germany and the United States generate more GDP per joule, around three to four megajoules per dollar, reflecting higher industrial efficiency, advanced technology, and stronger energy management. India and China, by contrast, use significantly more energy per dollar of GDP, which suggests greater reliance on heavy industry and lower efficiency in production systems. Japan lies between these two groups, balancing energy efficiency with limited domestic resources. Overall, the results demonstrate that differences in energy intensity are driven less by political or regional factors and more by how economies are structured, what sectors dominate, how efficient the capital stock is, and how energy is priced and managed. In short, this study finds that while countries vary in efficiency, the fundamental relationship between energy use and economic output holds steady: greater energy consumption consistently corresponds with greater GDP.

© Nathan Wang. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

References

[1] "BP Statistical Review of World Energy 2022," British Petroleum, June 2022.

[2] "Gross Domestic Product 2021," World Bank, 2021

[3] A Bonnet, "Energy Usage vs. GDP in the Context of Climate Change," Physics 240, Stanford University, Fall 2024.