Plans to boost the Philippines' coal-fired power capacity by more than 25 percent in just three years will be a cheap solution to the country's precarious power supply but bad news to investors in clean energy.

A total of 25 coal-fired power stations are in the pipeline with capacity totalling 12,200 megawatts, according to an updated list of power projects published by the Philippine Department of Energy in July. Twelve of them with a total capacity of 3,400 MW are under construction, and are slated to be completed by 2018. Those plants require at least 10 million tonnes of coal a year, industry estimates show.

About a third of the country's power capacity of nearly 18,500 megawatts uses coal as fuel, but supply from local mines mainly owned by Semirara Mining and Power Corp is not enough. Coal imports soared to a record 15.2 million tonnes last year. While miniscule compared to purchases by China and India, growing Philippine imports will be welcomed by Indonesia, its traditional main supplier, at a time prices are falling. The Philippines also buys coal from Australia, Vietnam and China.

"A significant portion of our electricity market is dependent on imported coal from Indonesia. I'm worried about our energy security being put in the hands of another country," said Vincent Perez, a former Philippine energy secretary who is now the CEO of wind power developer Alternergy Partners.

Promoting solar, wind, hydro and geothermal energy has become a challenge for investors as the government remains biased towards low-cost power from coal. Investors have been grappling with high initial expenses and red tape. But Theresa Cruz-Capellan, chief executive of SunAsia Energy Inc and president of the industry group Philippine Solar Power Alliance, says the additional coal-fired power plants should not be seen as lost opportunity for renewable-energy investors. "By the time they have built those coal-fired plants, we believe there will be additional demand and we can install additional capacity in just six months."