A new system requiring the installation of solar panels on newly built homes in Tokyo took effect on April 1, 2025. 

Tokyo has implemented an ordinance mandating the installation of solar panels on newly built detached homes and other new residential properties. This initiative is a key policy of Governor Yuriko Koike, aims to achieve “Carbon Half,” a goal to cut greenhouse gas emissions by half compared to 2000 levels by 2030. The ordinance was enacted in 2022 and has now been implemented after a roughly two-year preparation and awareness period.

The requirement applies not to homebuyers but to large-scale home builders that supply a designated number of new homes. These home builders must meet an assigned “total power generation quota” based on the number of units they supply, rather than installing panels on every single home.  The Tokyo Metropolitan Government will monitor and publish each builders’ progress annually on its website. The mandate applies to newly built detached homes and similar properties, but not to existing homes.

To support smaller home builders not subject to the mandate, Tokyo is offering subsidies to companies developing or improving energy-efficient homes. Additionally, financial support is available for construction firms working on enhancing design and construction techniques. 

Tokyo will publish home builders’ implementation status and may issue warnings or disclose violations if necessary to ensure compliance.  The city also plans to promote the adoption of high-performance solar panels suited to urban environment. Tokyo estimates the initial cost of installing a 4-kilowatt solar panel system at ¥1.17 million (approximately $7,800). This cost is expected to be recovered in approximately 13 years through income from selling electricity. However, if homeowners take advantage of a ¥100,000 (about $670) subsidy per kilowatt, the payback period could be reduced to around eight years. Furthermore, Tokyo’s official website introduces a program where businesses cover the initial installation cost and recoup their investment through electricity sales or equipment leasing fees. This allows homeowners to install solar panels with “zero initial cost”.

While the financial benefits of solar panel installation are projected to materialize over time, homeowners should also account for regular maintenance, equipment upgrades, and potential repair costs.

Although the system mandates solar panel installation on all new homes, exceptions exist. If a property is located in an area with poor sunlight exposure or lacks sufficient roof space for installation, the home builders will determine feasibility based on factors such as solar access and building design. Properties with north-facing roofs or small roof areas may be excluded from the requirement.