Carbon Dioxide Emissions Reduction Potential in Japan’s Power Sector

This report by the Stockholm Environment Institute, prepared for WWF-Japan, evaluates the potential for carbon dioxide (CO2) emissions reductions in Japan's power sector between 2000 and 2020. It compares a 'Business As Usual' (BAU) scenario, based on current trends and government projections, with a 'Power Switch' (PS) scenario characterized by aggressive transitions to non-fossil and low-carbon fuels and broad implementation of energy efficiency measures. The analysis demonstrates that the PS scenario can significantly reduce greenhouse gas (GHG) emissions with a relatively minor net cost to society, primarily by substituting natural gas for coal, phasing out nuclear power, and expanding renewable energy.

• The 'Power Switch' (PS) scenario can achieve a 31 percent reduction in annual greenhouse gas (GHG) emissions relative to the 'Business As Usual' (BAU) scenario by 2020. In absolute terms, the PS scenario reduces emissions by 94 million tonnes of CO2 equivalent per year by 2010 and 190 million tonnes per year by 2020, totaling nearly 2.0 billion tonnes of CO2 equivalent between 2000 and 2020.
• The net cost of implementing the Power Switch scenario from 2000 to 2020 is estimated at approximately 1.1 trillion yen, which equates to about 57 billion yen per year. This cost is calculated by factoring in additional capital investments in the electricity supply and demand sectors against savings in fuel import costs. On a per-unit basis, the net cost is 850 JPY per tonne of CO2 equivalent, roughly equivalent to a 0.3 percent tax on electricity consumption.
• The Power Switch scenario relies heavily on demand-side energy efficiency and distributed generation to reduce the need for power. By 2020, these measures are estimated to reduce electricity demand by 238 TWh. Consequently, net electricity consumption in the PS scenario for 2020 is 930 TWh, a 20 percent reduction compared to the BAU scenario.
• A central component of the PS scenario is the reduction of coal-fired generation, which is the most carbon-intensive option. The scenario proposes retiring 24 GW of coal-fired capacity by 2020, with approximately 16 GW retired between 2010 and 2020, and includes no additions of new conventional coal-fired plants.
• The PS scenario advocates for a gradual nuclear phase-out, assuming a plant lifetime of 40 years. Under this plan, 10 GW of existing nuclear capacity would be retired by 2020, while only 6.9 GW of plants currently under construction or in the planning phase would be added.
• The PS scenario emphasizes the aggressive deployment of renewable energy, targeting a supply-side electricity generation share of 13.5 percent in 2010 and 18.1 percent in 2020. When including demand-side distributed photovoltaic (PV) systems, total renewable generation would reach 13.9 percent of total output by 2010 and 18.9 percent by 2020.
• Natural gas is positioned as a critical interim fuel to reduce CO2 emissions over the next 20 years. The PS scenario utilizes high-efficiency combined-cycle plants and cogeneration to replace declining coal, oil, and nuclear capacities, while viewing natural gas as a transition toward a long-term reliance on renewable resources and hydrogen.
• The PS scenario improves Japan's energy security by diversifying the fuel supply and reducing reliance on imports. By 2020, it results in a nearly 70 percent reduction in coal imports relative to the BAU scenario, as well as decreases in crude oil (3 percent) and nuclear fuel (20 percent) imports.

APA

Nakata, M., Oda, J., Heaps, C., & Von Hippel, D. (2003). Carbon Dioxide Emissions Reduction Potential in Japan’s Power Sector. Stockholm Environment Institute. https://cdn.leap.sei.org/documents/PowerSwitchJapan.pdf

Chicago

Nakata, Masami, Junichiro Oda, Charles Heaps, and David Von Hippel. Carbon Dioxide Emissions Reduction Potential in Japan’s Power Sector. Stockholm Environment Institute, 2003. https://cdn.leap.sei.org/documents/PowerSwitchJapan.pdf.

Wikipedia

{{cite report |last1=Nakata |first1=Masami |last2=Oda |first2=Junichiro |last3=Heaps |first3=Charles |last4=Von Hippel |first4=David |title=Carbon Dioxide Emissions Reduction Potential in Japan’s Power Sector |publisher=Stockholm Environment Institute |date=October 2003 |url=https://cdn.leap.sei.org/documents/PowerSwitchJapan.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{nakata2003carbon, author = {Nakata, Masami and Oda, Junichiro and Heaps, Charles and Von Hippel, David}, title = {{Carbon Dioxide Emissions Reduction Potential in Japan’s Power Sector}}, institution = {Stockholm Environment Institute}, year = {2003}, month = oct, url = {https://cdn.leap.sei.org/documents/PowerSwitchJapan.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }