Many new homes built in Tokyo will require solar panels to be installed starting in April 2025, Kyodo News has reported. The local assembly passed new regulations requiring major construction companies to equip homes smaller than 2,000 square meters (21,500 square feet) with solar panels or other renewable power sources. The measure is the first of its kind in Japan and aims to cut the city’s carbon emissions in half. 

The government estimates that the 980,000 yen ($7,200) price of a 4kW installation can be recouped in about six years based on utility bill savings and an existing 100,000 yen ($728) per kW grant. Leasing costs will also be reduced through other subsidies, according to an information-packed slide deck (PDF)

The measure applies only to around 50 builders who supply over 20,000 square meters (215,000 square feet) to the market, so it’s not clear what percentage of new homes will fall under the new rules. The measure should have a major effect, though, as the Tokyo government estimates that half of existing buildings (70 percent of which are homes) will be replaced with new construction by 2050. 

New construction starts in Japan averaged around 800,000-900,000 per year from 2012 to 2021, and a handful of major contractors called Super Zenecon dominate the construction sector, according to Statista

Japan is the world’s fifth largest producer of carbon emissions, but has promised to be carbon neutral by 2050. It’s not the only country mandating solar installations. In France, lawmakers recently approved a bill requiring parking lots with a minimum of 80 spaces to be covered by solar panels. The French government said the plan, aimed primarily at parking lots off freeways and major routes, could generate up to 11 gigawatts — the equivalent of 10 nuclear reactors.