Indonesia's Sinar Mas Group, the Widjaja family's energy-to-banking conglomerate, is planning to list power assets in an initial public offering (IPO) of up to US$800 million (S$1.13 billion) in Singapore, in what could be the country's biggest IPO in four years, according to the Wall Street Journal.

The group is planning to bundle the assets into a business trust and launch the IPO in the first half of next year, the Journal reported on Thursday, quoting people familiar with the matter.

The IPO is one of the options before the company to expand its power plants, managing director Gandi Sulistiyanto told the Journal.

This is in order to participate in the Indonesian government's plan to add 35,000 megawatts to the country's power capacity in the next three years.

Sinar Mas plans to raise between US$600 million and US$800 million from the sale and bankers have already begun sounding out investors.

At the top end, the IPO would be the biggest for Singapore since the May 2013 launch of Asia Pay Television Trust by cable-TV operator Taiwan Broadband Communications, which raised US$824 million.

A final decision has not yet been reached on which of the conglomerate's assets will be included in the trust, the Journal added.

Sinar Mas' energy and infrastructure unit, Dian Swastatika Sentosa, has operations in power and steam generation, coal mining and chemical trading, among other activities.

The conglomerate's other businesses comprise pulp and paper, agribusiness and food, financial services, real estate development and telecommunications.