In October 2021, Japan decided to strengthen its measures against global warming to achieve carbon neutrality by 2050 and reduce greenhouse gas emissions by 46% by 2030 (compared to 2013). In line with this, energy-saving measures in the building sector, which accounts for about 30% of Japan’s energy consumption, are urgently needed.
In April this year, the revised Building Energy Conservation Act came into effect, raising standards, including building insulation performance, and requiring all new buildings to comply with energy conservation standards. Ahead of the national government, ICLEI member cities, the Tokyo Metropolitan Government, and Kawasaki City have begun mandating the installation of solar power systems under their ordinances.

Solar power panels are mandatory in Tokyo and Kawasaki

Tokyo is the first local government in Japan to implement a system requiring the installation of solar power panels in newly built homes and buildings (with a total floor area of less than 2,000 square meters), ensuring insulation and energy-saving performance, and installing EV chargers, using a dedicated subsidy scheme.
The obliged installers of solar power panels are major housing suppliers (approximately 50 companies will be subject to this mandate) that supply over 20,000 square metres of housing per year in the metropolitan area.
This initiative supports Tokyo’s goals of achieving Zero Emission Tokyo by 2050 and Carbon Half by 2030, and a new goal of reducing greenhouse gas emissions by at least 60% from 2000 levels by 2035.
You can learn more information on the Tokyo Metropolitan Government website.

Kawasaki, as well as Tokyo, started enforcing the mandatory installation of solar power panels in April 2025. Kawasaki is developing various initiatives to decarbonize the city area, including positioning initiatives with particularly high project effectiveness as the ‘Five Major Projects’ in ‘the Kawasaki City Basic Plan for the Promotion of Global Warming Countermeasures’. One of the projects is the establishment of the ‘Integrated Promotion Project for Building Solar Power Generating Equipment’, which requires the installation of solar power panels in buildings. This installation obligation applies to major housebuilders and other construction companies that build new buildings (including detached houses) with a total floor area of less than 2,000 square metres in the city. The city has secured 800 million yen in subsidies for solar power panel installations in fiscal 2025, four times more than in fiscal 2024.
Further information can be found on the Kawasaki Solar Information Dissemination Site.

Cities around the world are working towards achieving a decarbonized society by 2025, and the introduction and expansion of renewable energy is one of the key initiatives to achieve this. It is believed that the initiative to make the installation of solar power mandatory will spread to other Japanese local governments in the future.