Top Indonesian coal miners like Bumi Resources are expected to report strong results for the first half of this year, with higher coal prices more than offsetting increasing costs of production from a jump in fuel prices.

“Fuel prices are rising, but Bumi expects its cash margins to continue increasing as coal prices are expected to rise far more than the input costs,” said Dileep Srivastava, a director at Bumi. “Hence, we expect an outperformance in operations for fiscal year 2011 and going forward.”

Bumi, the country’s largest coal producer and the world’s biggest exporter of thermal coal, booked a 35 percent increase in revenue to $2.7 billion in the first half, even though output remained steady from a year earlier at 30 million tons. The coal, however, was sold at an average realized price of $91 per ton, a 36 percent rise from the year before.

Other ratios such as gross margins, operating profit, net income and earnings before interest, tax, depreciation and amortization (ebitda) are expected to be sharply up in the first half of this year, Dileep said. Bumi will report its audited income statement for January to June by the end of next month.

“With global coal supply falling far short of burgeoning demand from China, India and Indonesia, and with a small short-term offset from Japan, the forward price curves indicate that benchmark coal prices will continue to be strong, ranging between $122 per ton FOB presently and rising conservatively to $133 per ton FOB over the medium term,” Dileep said.

This prompted a bullish outlook that full-year financial performance could surpass expectations. This year, Bumi expects production sales to reach 65 million to 66 million tons at an average price of $90 per ton FOB. That is compared to last year’s 60 million tons at $71 per ton FOB.

“All in all, 2011 and beyond we are eyeing prospects of a major outperformance,” Dileep said.

Separately, Adaro Energy, the country’s second-largest coal producer, is forecast to book a 58 percent increase in revenue in the first half, said Reza Priyambada, an analyst at Indosurya Asset Management in Jakarta. The miner has not yet announced its first-half results.

Adaro said its coal sales rose 10 percent to 24.02 million tons in the first half of this year from 21.75 million tons in the same period last year. The company has set a production target of up to 48 million tons.

“We are on the right track this year,” Garibaldi Thohir, its president director, said on Friday. “Coal production is above last year’s production.”

Thohir said rising coal sales were expected to boost the company’s revenue.

Adaro’s coal sales increased 20 percent in the second quarter this year from the first quarter as the company booked purchase agreements with several countries including India, China, South Korea and Thailand, which became its newest customer in the second quarter of this year.

Global coal prices may rise more than 5 percent next year as surging demand from China and India benefits mining companies like Berau Coal and Indo Tambangraya Megah, an industry group said on Friday.

The price of thermal coal is expected to rise to $130 per metric ton by the end of this year and remain high into 2012, said Bob Kamandanu, chairman of the Indonesian Coal Mining Association (APBI).

“Winter triggers the increase in coal demand, but the supply could be short by the end of this year,” Bob said. “That is why the coal price is likely to accelerate.

“Coal companies usually use this year’s coal price as a benchmark to sell next year’s coal sales contract,” he added.

Thermal coal was at $120.95 per metric ton on the globalCOAL Newcastle index, the benchmark for Asian utilities, at Friday’s close. It reached a high of $140 in January when prices were pushed up by floods in Australia’s eastern Queensland state.

Coal companies will try to take advantage of the high price by producing more coal, Bob said.

Output increased 10 percent to 188 million tons in the first half this year, up from 171 million tons in the same period last year. Most of Indonesia’s coal production is thermal.

Total 2011 coal output is estimated to increase 20 percent to 360 million tons from last year, according to the association, but could go higher if the weather is favorable in the seond half.

Bob estimates China’s demand for coal doubling from 3 to 6 billion tons in the next five years. India’s demand is projected to exceed 1 billion tons by then, up from 600 or 700 million tons this year.

Demand from other nations, including Vietnam, will further drive up the price, Bob said.

State-run PetroVietnam plans to build a power plant that will use coal from Indonesia and Australia, and media reports indicate that Jaks Resources of Malaysia has been licensed to build one in northern Vietnam.

Berau Coal, one of the largest mining companies in Indonesia, projected its output would increase 25 percent from 20 million tons this year to 25 million tons next year.

Meanwhile, Indo Tambangraya Megah , a unit of Thai’s Banpu, forecast its coal production to increase 10 percent to around 28 million tons next year from this year’s target 25 million tons.

“With higher sales volume and higher prices, ITM’s revenue and bottom line will be higher,” said Edward Manurung, finance director at ITM.