Essar Energy's profit dented by higher costs, weak Indian rupee

* Current price EBITDA falls 7 percent

* Revenue rises 5 pct

* Shares fall 7 pct, biggest FTSE-250 percentage loser

Nov 25 (Reuters) - Essar Energy Plc reported a first-half loss as a weak rupee and costs from power projects in 2012 offset a rise in the Indian power plant operator and oil refiner's revenue.

Essar's London-listed stock fell as much as 7.6 percent in value to its year-low on Monday morning, making it the biggest percentage loser on the FTSE-250 index.

The power, oil and gas arm of privately held Indian conglomerate Essar Group posted a current price pretax loss of $44.4 million in the six months ended Sept. 30, compared with a profit of $52.7 million a year earlier.

Essar blamed depreciation and interest charges from its Maham and Vadinar power projects in 2012 for the hit, prompting JP Morgan Cazenove analyst Nitin Sharma to cut his full-year net earnings estimate to $10 million from $51 million.

Essar also said it had taken a $483 million loss from the rupee's depreciation, the majority of which was unrealised.

The rupee hit a spate of record lows in August, but began to stabilise the following month after a series of measures by India's central bank. The rupee shed about 9 percent from when it began falling in August to the end of September.

Essar Energy also said that it would dispose of some non-core assets to improve margins, cash flow and profitability.

REFINING MARGINS RISE

At Essar's Vadinar refinery, which underwent an expansion last year, current price refining margins rose 9 percent to $6.97 per barrel, driven by further operational improvements and lower input oil prices during the period.

Brent prices fell as much as 12 percent during Essar's first half amid dwindling geopolitical concerns about Iran, increased Libyan production, and the U.S. agreeing to call off military action against Syria.

"Further work is now under way at Vadinar to boost margins by an additional $1.50 per barrel over the next three years," Essar said in a statement, adding that the changes included a new hydrogen making unit and improved efficiency measures.

Essar Energy runs Vadinar in the western-Indian state of Gujarat through its Essar Oil (BSE: ESSAROIL.BO - news) unit, India's second-largest private refiner. Most of Vadinar's output is middle distillates such as diesel, gasoil, jet fuel and kerosene.

In June, Essar forecast a 7 percent rise in India's annual diesel demand, and a 5 percent growth in gasoline demand.

The Indian government had eased its price-control mechanism for diesel this year, allowing state-run fuel retailers to increase prices gradually.

Essar Energy said current price refining margins fell 37 percent to $5.03 per barrel at its Stanlow refinery in Britain, dragged down by imports from the United States, Russia and the Middle East that impacted light distillate and fuel oil cracks.

The company undertook a major turnaround at Stanlow earlier this year, refurbishing its catalytic cracker at a cost of around $35 million, to give the unit another 25 years of life.

Essar's current price earnings before interest, tax, depreciation and amortisation (EBITDA) fell 7 percent to $543.7 million. Revenue rose 5 percent to $13.4 billion.

Essar shares were down 6.6 percent at 94 pence at 1212 GMT.