Tokyo Electric Power Co. is set to raise 50 percent more through bond sales than it had planned because borrowing costs remain low in Japan, according to a company official.

Tepco approved plans at a board meeting last week to sell as much as ¥200 billion in bonds by March, said the finance official, who asked not to be identified before an announcement.

Tepco has raised the ¥400 billion it targeted from bond sales for the fiscal year ending next March. It sold bonds ahead of schedule because a fall in Japanese government bond yields reduced the cost of raising funds, the official said.

Companies including Tepco and NTT Corp. offer a premium, or spread, to government bond yields to attract investors to their securities and compensate them for the perceived risk of a default.

Japan's 10-year bond yields reached 1.5 percent Sept. 10, the lowest since February 2006, on speculation losses tied to U.S. subprime mortgage defaults will prompt the Bank of Japan to delay raising interest rates.

The company sold ¥329 billion of bonds last year, about 32 percent more than it targeted, he said.