Tokyo Electric Power Co. Holdings Inc. could become the first Japanese utility to issue green bonds.

The company is considering raising funds via its new Tepco Renewable Power Inc. unit, established this month to take over its renewable energy business, according to spokesman Takao Takagi. Details such as the timing, size and currency are still being discussed, he said.

Tepco has been increasing its bond sales since returning to the debt markets in 2017, six years after the Fukushima nuclear disaster, because investors have been attracted to its relatively high-yield premiums.

Japanese utilities, which are among the biggest sellers of yen corporate notes, haven't sold green bonds so far, and their introduction may depend on progress in the country's usage of renewable energy sources.

Yen-denominated environmental, social, governance and green bond sales in Japan are expected by some bankers to surpass ¥1 trillion ($9 billion) next year. That compares with ¥795.5 billion so far this year, after ¥353 billion in 2018, according to data compiled by Bloomberg. The nation's green note issuance is still limited to a few sectors such as finance, construction and leasing.