SAO PAULO, Dec 14 (Reuters) - Brazilian energy firm Ambar Energia is set to buy electric utility Copel's 81.2% stake in natural gas-fired power plant UTE Araucaria for 320.7 million reais ($65.24 million), the firms said on Thursday.

The facility, located in the southern state of Parana, has an installed generation capacity of 484.15 megawatts (MW).

($1 = 4.9155 reais) (Reporting by Peter Frontini; Editing by Kylie Madry)