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ndonesian coal-mining giants PT Adaro Energy (ADRO) and PT Berau Coal Energy (BRAU) saw their net profits more than doubled last year on the back of higher selling prices.

The nation’s largest coal miner, PT Bumi Resources (BUMI), however, recorded a net loss last year despite growing revenues from sales — benefiting from the surge in selling prices — due to soaring costs.

Indonesia, the world’s largest exporter for thermal coal that ships to big emerging markets like China and India, has been reaping the benefits from the coal prices boom. Coal stocks have also become among the most heavily-traded in the stock exchange, a bourse executive said.

Adaro, the nation’s second-largest coal miner, booked a US$552 million net profit in 2011, 123.7 percent higher than the $247 million recorded the previous year, the company said in a statement on Wednesday.

“Net income benefited from strong production-volume growth, robust average selling price and continued cost control,” Adaro said in a press statement.

Adaro’s production and sales volumes rose 13 and 15.8 percent respectively, to 47.67 and 50.78 million tons. That, coupled with a 27.6 percent increase in the average selling price, boosted net revenues by 46.7 percent to $3.99 billion.

Cost of revenue grew 35.5 percent to $2.6 billion, a “moderate increase” compared to Adaro’s faster revenue growth.

“The combination of normal weather, arrivals of new and larger-sized heavy equipment and our contractors’ high-quality performance enabled us to achieve the higher end of our production target.”

Adaro is looking to grow its production volume from 4.89 to 11.81 percent this year, to between 50 and 53 million tons, to maintain earnings before interest, taxes, depreciation and amortization (EBITDA) — a measure of profitability — at $1.2 billion to $1.5 billion.

Berau, which is affiliated with the Bakrie Group conglomerate, also saw a surge in revenues derived from sales, with an increase of 57.06 percent to $1.66 billion.

“Despite high levels of rainfall, Berau mined 19.4 million tones of coal, a 12 percent increase over 2010,” said Bumi Plc., which owns a 85 percent stake in Berau, in a statement submitted to the London Stock Exchange.

Sales rose 16.96 percent to 20 million tons, and a 30.58 percent rise in selling price to $38 per ton, boosted Berau’s bottom line.

With costs of goods sold (COGS) growth slower at 45.84 percent, amounting to $1 billion, and other expenses remaining manageable, Berau’s profits jumped 133.57 percent to $160.82 million.

Shares in Adaro and Berau soared following the earnings announcement. Berau’s stock surged 7.84 percent to Rp 550 a piece, the highest level in seven months. Adaro gained 2.2 percent to Rp 1,930 per share.

Bumi Resources, however, posted a net after-tax loss of $119 million in the 10 months ending Dec. 31. Despite a 32 percent increase in the selling price to $93.3 per ton, its soaring operating costs ate into the company’s profit potentials.

“Higher fuel and contractor costs, along with an increase in the stripping ratio, were the principal reasons for the increase in production costs,” Bumi Plc., which owns a 29 percent stake in Bumi Resources, said in a statement.

It mined 65.9 million tons of coal in 2011, up 9.11 percent from 2010.