Japan, the world’s fifth largest carbon emitter, has committed to achieving climate neutrality (a balance between the emissions captured and released) by 2050 — a difficult goal considering its deep reliance on coal-burning thermal power. But the country seems to be betting big on solar power, asking for all new homes in Tokyo to add panels.

Tokyo is the largest city in Japan, and arguably, in the world. Some 39 million people call Tokyo’s urban area home, and the city alone has greenhouse gas emissions comparable to many countries. Japan’s road to sustainability will start in Tokyo but if Japan really is serious about its sustainability plans, it has to start as early as possible.

This new decision, the first of its kind for a Japanese municipality, requires 50 major construction firms to equip homes of up to 2,000 square meters in Tokyo with solar power panels to bring down carbon emissions. It will be applicable starting in 2025. Currently, only 4% of the buildings in Tokyo have solar panels on them.

The city government estimates that installing solar panels on every new house will involve an average initial investment of $7.200 — but that cost will be made up in 10 years’ from electricity sales revenue, and will then continue to produce value. The government has also said it will allocate a specific budget to subsidize the costs of solar panels for home buyers.

A big move toward solar power

The ruling Liberal Democratic Party, the largest one in Tokyo’s assembly, opposed the new rule as “residents had not fully understood or accepted it.” However, all the other parties have approved it, including the Japanese Communist Party, the local Tomin First no Kai party and the coalition partner of Japan’s ruling party – the Komeito.

“In addition to the existing global climate crisis, we face an energy crisis with a prolonged Russia-Ukraine war,” Risako Narikiyo, a member of Tomin First no Kai, said at the moment of the vote in the Tokyo’s Assembly earlier this week. “There is no time to waste.”

Globally, solar power seems like the world’s best bet for energy. Solar power generation rose 22% last year and it’s quickly becoming the lowest-cost option for new electricity generation in most parts of the world. The International Energy Agency expects rooftop solar on buildings to grow due to higher retail electricity prices.

The decision in Tokyo isn’t without precedent — in fact, it’s becoming more and more common across the world as policymakers see rooftop solar as a key component of a sustainable energy mix. Solar panels mandatory will also be mandatory on all new European Union homes from 2029 onwards. The rule will first be applicable to new government buildings and then to all, including residentials. The same goes for California. Last year, the state’s Energy Commission approved a new rule that requires solar panels and battery storage in new commercial buildings and specific residences starting in 2023. The buildings included in the proposal are hotels, offices, retail and grocery stores, schools and civic spaces such as convention centers. Switzerland is also doing it.

It remains to be seen whether Japan’s strategy will pay out; this is an encouraging step, but on its own, it won’t be enough. For now, Tokyo’s metropolitan government aims to cut greenhouse gas emissions by 50% by 2030, compared with 2000 levels.