Tokyo Hopes Rooftop Solar Mandate Will Help It Get Through Hot Summers

livemint.com:

solar panels on new single-family homes to get some breathing room—even if it has to buy most of the panels from China. The policy in one of the world’s largest metropolises is a test case for whether solar power makes sense on urban rooftops. The idea has long drawn attention as a way to fight global warming but has advanced relatively slowly worldwide, apart from a rooftop solar mandate in California pushed by Democratic Govs.

Jerry Brown and Gavin Newsom. “We need to prepare to protect not only our national security, but also the energy security of individual households," Tokyo Gov. Yuriko Koike, the architect of the mandate, said in an interview.

Koike has had panels on her own house for a decade. As a government minister, she created a “Cool Biz" plan that led Japanese salarymen to ditch suits and ties in summertime so they could keep the thermostat higher. In the Land of the Rising Sun, Koike said, “we unfortunately aren’t rich in oil and gas, but wouldn’t it be fitting if we could instead harness the sun?" Proponents say more rooftop solar would help on hot summer days when electricity demand peaks, and make the city resilient if an earthquake or typhoon knocked out the power grid.

The downsides: More solar also means higher electricity bills, including for lower-income apartment dwellers, because homeowners with rooftop panels can sell their excess power to the grid at an above-market rate. Even with the mandate, solar power generated in Tokyo is projected to supply only 4% of the city’s electricity in 2030. “We cannot have a sufficient amount of power generation just by having solar panels on limited rooftops," said Tatsuya Terazawa, head of the government-affiliated Institute of Energy Economics, Japan.