Abstract Considering the unclear nuclear future of Japan after Fukushima Dai-ichi nuclear power plant accident since Mar. 11, 2011, this study assesses a series of energy consumption scenarios including the reference scenario, nuclear limited scenarios and current nuclear use level scenario for Japan in 2030 by the G-CEEP (Glocal Century Energy Environment Planning) model. The simulation result for each scenario is firstly presented in terms of primary energy consumption, electricity generation, CO2 emission, marginal abatement cost and GDP (gross domestic product) loss. According to the results, energy saving contributes the biggest share in total CO2 emission reduction, regardless of different nuclear use levels and different CO2 emission reduction levels. A certain amount of coal generation can be retained in the nuclear limited scenarios due to the applying of CCS (carbon capture and storage). The discussion indicates that Japan needs to improve energy use efficiency, increase renewable energy and introduce CCS in order to reduce the dependence on nuclear power and to achieve CO2 emission reduction target in 2030. In addition, it is ambitious for Japan to achieve the zero nuclear scenario with 30% CO2 emission reduction which will cause a marginal abatement cost of 383 USD/tC and up to −2.54% GDP loss from the reference scenario. Dealing with the nuclear power issue, Japan is faced with a challenge as well as an opportunity.