The Tokyo Metropolitan Government (TMG) will subsidize a vast expansion of the use of solar power as part of its 10-Year Carbon–Minus Tokyo Project, which aims to reduce carbon dioxide emissions in the area. The plan was revealed in an interim report compiled by a TMG study panel and released in October 2007. TMG hopes to encourage house and apartment owners in Tokyo to introduce solar power equipment that can produce a total of about one million kilowatts; to this end it will set up a green certificate system for trading the environmental value of electricity generated by private homes using photovoltaic (PV) systems. (See the related website below.)

The report recommends setting up an official green power certificate system as soon as possible as a way of expanding solar power use by providing an economic incentive to individual PV system owners. It also suggests that PV system manufacturers and home builders should implement cost reduction measures, and that financial institutions offer preferential interest rates, so that the initial investments made by individual PV owners can be recouped in about 10 years.

To further promote solar heat utilization, the report suggests establishing a system to evaluate and certify the performance of solar-thermal products. It also calls for supporting the creation of a green heat certificate market to clarify the value of the economic benefits resulting from environmental improvements due to carbon dioxide emission reduction from solar heat utilization.

As TMG considers solar energy the most essential measure for reducing household greenhouse gas emissions, it will initiate the various approaches proposed by the study panel in fiscal 2008, aiming to attain its target of reducing emissions by 25 percent compared to 2000 levels by 2020.