The regulation - passed by the Japanese capital’s local assembly on Thursday - requires 50 major construction firms to equip homes of up to 2,000 square metres with renewable energy power sources."In addition to the existing global climate crisis, we face an energy crisis with a prolonged Russia-Ukraine war," said Risako Narikiyo, a member of the local assembly.The city’s Metropolitan Government aims to halve greenhouse gas emissions by 2030 compared with 2000 levels, and to be emission-free by 2050.Just four per cent of buildings with the capacity for solar panels currently have them.The 4 kilowatt panels will cost around 980,000 yen (€6,725) to install, but the government estimates that this will be covered by electricity sales revenue within 10 years."