UPDATE 1-India's Tata Power posts surprise loss

* Q2 loss after higher interest, depreciation, forex charge

* Lower revenue from coal business impacts bottomline

Nov 6 (Reuters) - India's Tata Power Company Ltd posted a surprise second-quarter loss, hit by higher finance and depreciation costs at its power projects and lower revenue from its coal units.

The company, which operates 6,899 MW generation capacity, said its bottomline was mainly impacted by an additional impairment charge of 2.5 billion rupees ($45.8 million) due to a change in the long-term foreign currency outlook at its western India plant.

It has so far commissioned 2,400 MW out of a 4,000 MW power plant it is building at Mundra in western India. The project, which runs on imported coal from Indonesia, has been suffering from mounting losses after the South East Asian nation last year raised levies on coal exports.

Tata is unable to pass on the cost increase on imported coal, but has asked India's central electricity regulator for a tariff hike. It is still awaiting a decision.

The company posted a consolidated net loss of 838 million rupees, compared with a net loss of 11.9 billion rupees a year earlier. Revenue rose 22 percent to 76.5 billion rupees, helped by the commissioning of new units.

Analysts had expected Tata Power to post a net profit of 2.46 billion rupees, according to Thomson Reuters I/B/E/S.

The company said pre-tax profits at its power business jumped 55 percent to 7.2 billion rupees, mainly due to three new units it started this year.

Tata Power, which also co-owns two mines in Indonesia along with Bumi Plc, said its coal mining business saw pre-tax profits fall 51 percent to 2.9 billion rupees as global coal prices fell.

Tata Power shares closed 0.9 percent higher in a firm Mumbai market. The stock has gained 22 percent so far this year, matching a rise in the main stock index.