UPDATE 1-Huaneng Power back in profit, warns of coal prices

* Huaneng H1 profit 1.87 bln yuan vs 1.61 bln yuan consensus

* Huaneng warns of tight coal supply in H2

* Huadian H1 profit 545 mln yuan vs 515 mln yuan consensus

(Recasts, adds details)

HONG KONG, Aug 11 (Reuters) - Huaneng Power International Inc (0902.HK), China's largest electricity provider, reported a return to profit in the first half of 2009, buoyed by two tariff hikes in the second half of last year and lower coal costs.

Huaneng (HNP.N) (600011.SS) said on Tuesday its net profit totalled 1.87 billion yuan ($273.6 million) for January-June, compared with a 543.8 million yuan net loss a year earlier, its first interim loss since its listing in Hong Kong in 1998.

The result was better than a consensus estimate for a 1.61 billion yuan profit from five analysts surveyed by Reuters.

But the power firm warned that while power generation appears resilient on the back of strong domestic economic growth, the outlook for the second half is still uncertain.

"For the second half of 2009, there are still risks of tight coal supply," Huaneng said in a statement. "As we have not signed coal contracts, the coal market is still fraught with uncertainty and instability. Coal supply and the price of coal could present new problems and challenges."

China's five major power generating groups have been in a tussle with coal miners since late last year in their annual supply talks. They have insisted on steady coal prices due to power price caps, while miners have asked for an increase because coal prices under long-term supply terms were below market rates and they faced higher tax charges.

Coal-fired power plants, which produce nearly 80 percent of China's electricity, suffered hefty losses last year during the global commodities boom.

Analysts believe the worst could be over for China's big independent power producers, which have been boosted by lower unit fuel costs and higher tariffs, even as power generation in China declined in the first half of the year.

Huaneng's smaller rival Huadian Power International Corp (1071.HK) (600027.SS) said on Tuesday its net profit totalled 544.8 million yuan for January-June. The power provider lost 506.3 million yuan in the same period a year ago.

The result was slightly higher than the 515 million yuan forecast by four analysts polled by Reuters.

China's Datang Power International Power Generation (0991.HK) (601991.SS) reports its earnings on Friday.

($1=6.834 Yuan)

(Reporting by Sui-Lee Wee, Editing by Mariam Karouny)