Abstract
In 2008 the first promise period of the Kyoto Protocol starts, and in the Japanese public welfare section, the energy saving and new energy introduction in the region is promoted in addition to that in the building. On the other hand, the contractor was organized and functioned on the assumption of receiving an order of the building construction, therefore it became a problem for the contractor to do environmental assessment etc. as a business which is necessary for energy saving and new energy introduction in the region. Now, in Japan the contractor establishes environmental assessment etc. as a business and is working on soft-ware development that can support such a business. In this report, as an example of the new approach of the contractor, the author reports the new business and software development for the decentralized energy system.