* First-half core profit 4.1 billion euros, down 0.9 percent
* Net profit beats forecasts on asset revaluations
* Sees 170 million euro 2013 pre-tax hit from energy reforms
* Says will be additional 90 mln euro hit from 2014
* Impact on renewable energy business still unknown
* Shares lose early gains
By Tracy Rucinski
MADRID, July 24 (Reuters) - Spanish utility Iberdrola said fresh energy reforms would wipe at least 170 million euros ($225 million) from pre-tax earnings this year, and potentially 260 million euros annually from 2014.
The estimates reflect government measures that will cap profits at Iberdrola's traditional generation business, but do not include the potential impact of caps and subsidy cuts on its renewable energy arm as details continue to be ironed out.
One of the world's biggest wind farm operators, Iberdrola was able to post stable first-half core profit on Wednesday despite higher costs in Brazil and a new power generation tax largely thanks to strength at its renewables division.
But a new energy sector overhaul, announced on July 12 and designed to plug a widening gap between regulated power prices and costs, includes a series of measures that will hit both Iberdrola's traditional power and renewable businesses.
Iberdrola Chairman Ignacio Galan called the reform "unfair" and said the company would fully evaluate the impact on its green energy business once all of the details are known, probably in October.
Iberdrola's shares gave up early gains to trade flat at 3.99 euros by 1155 GMT. The stock was trading at a price-to-earnings ratio of 10.36, in line with sector peers.
Like other Spanish utilities, Iberdrola's profitability has already been hit by weak energy demand in a recessionary economy and previous reforms aimed at plugging a 26 billion euro ($34.37 billion) tariff deficit, including a recent 7 percent tax on power generation.
Iberdrola blamed that levy for an 0.9 percent year-on-year decline in first-half earnings before interest, taxes, depreciation and amortisation (EBITDA) to 4.1 billion euros, despite a 10.5 percent rise in profit at its renewables arm.
The company said it paid 79 percent more in taxes and levies in the six months to June versus a year earlier, reflecting the new generation tax and energy efficiency programmes in Britain, where it owns Scottish Power.
Net profit beat analyst forecasts with a 2 percent decline to 1.7 billion euros after the company took advantage of a new law on corporate taxation that allowed it to re-value assets in order to secure future deductions.
The one-off tax income offset an impairment charge on assets in Canada and the United States, where Iberdrola said its wind business is facing increased competition from shale gas.
Iberdrola said it still plans to sell a further 800 million euros of assets as part of a 2012-2014 strategy to secure its credit ratings and reduce debt, which reached 28.8 billion euros at June 30, down 5 percent from 2012.
Operating cash flow, an indicator of disposable funds, fell 3.9 percent to 3.2 billion euros in the first half from a year ago.