Utilities like gas and electricity companies are reasonable investments without high risk in Japan. The main reason is that those markets are still regulated and the underlying cashflows are relatively stable and predictable. Long term investors like insurance companies are a main source for their funding.
In a ranking regarding stability and credit worthiness utility companies rank behind government agency bonds and municipalities. The income stream is quite predictable and the information published is normally also in English available. Adjustment clauses for the companies are mostly in the companies favor and mitigate market price risk. Price risk has to be taken by the customer. This price risk is dampened by the relatively high share of nuclear energy domestically generated. Renewable resources are picking up slowly, because the written-off nuclear power plants can produce energy relatively cheap and opposition against nuclear power is quite weak.
Main utility companies are:
Tokyo Electric Power www.tepco.co.jp/en/index-e.html
Osaka Gas Company www.osakagas.co.jp/ir/index_e.html
Kyushu Electric Power www.kyuden.co.jp/en_index.html
Kansai Electric Power www.kepco.co.jp/english/
Toho Gas Company www.tohogas.co.jp/eng_index/index.html
Ratings: All aforementioned electric and gas companies can be rated 'green'.