(Recasts with minister's comments on price, adds share prices)
By Antonio De la Jara
SANTIAGO, Aug 16 (Reuters) - The cost of energy in Chile is likely to fall in the next decade, as an auction aimed at providing around a third of the copper exporter's energy needs had attracted bids priced more competitively than forecast, the energy minister said.
The winners will be announced on Wednesday of the auction to supply a total of 12,430 gigawatts per hour annually for 20 years from 2021 and 2022, divided into five blocks.
But the offers ensured that energy prices would be "well below" $60 per megawatt-hour (MWH), less than half the cost of two and a half years ago, Chile's Energy Minister Maximo Pacheco told Reuters on Tuesday, after the envelopes of the bids were opened.
Share prices in Chilean energy companies fell on fears of an impact to profits. Enersis Chile, the local arm of Italy's Enel, fell 3.6 percent, while Colbun and AES Gener were both down around 3 percent.
The massive auction - the biggest in the country's history - has attracted 84 bids from home and abroad, including European firms Gas Natural, Ibereolica, Acciona Energia , AustrianSolar, wpd and Solairedirect.
Demand for energy has risen rapidly in Chile, which has among the highest power prices in Latin America and an energy-intensive mining industry that produces around a third of the world's copper, much of it from remote desert areas.
It has practically no hydrocarbons of its own, but ample potential for renewable energy. Solar energy generation in particular has expanded quickly in recent years, and many of the bids were from solar and wind power firms.
"We are very happy with the result price-wise, but also the fact that we are going to have cheaper and cleaner energy," said Pacheco.
Analysts had agreed that tariffs would probably fall as a result of the auction, pointing to likely aggressive offers from the large number of renewables firms participating.
"This will be one of the most competitive auctions in Chile's history, with bidders presenting offers almost seven times higher than the amount being auctioned," said ratings agency Fitch.
But the market had expected values closer to $80 per MWH.
Chilean state energy firm ENAP, which runs the country's two major oil refineries and which the government wants to expand, took part in the auction, but local newspaper Pulso reported that it bid $72.90, likely too high to be successful. (Reporting by Antonio de la Jara, Additional reporting by Fabian Cambero and Rosalba O'Brien; Editing by Alan Crosby and Chris Reese)