UPDATE 2-Chile Endesa 1st-half profit down on lower sales

* Falling electricity sales and prices hit earnings

* Share prices stable, up 1 pct on the day (Adds quotes and company background)

SANTIAGO, July 27 (Reuters) - Chile's leading electricity generator Endesa Chile END.SN (EOC.N), said on Tuesday its January to June net profit fell 37 percent compared with the same period last year on lower electricity sales and prices.

Santiago-based Endesa, which has generation plants throughout Latin America, posted a net profit of 208.5 billion pesos, or $384 million, in the first half of 2010, compared with 331.2 billion pesos or $613 million a year earlier.

"The decrease was explained by a 26.3 percent drop in operating income...given lesser electrical generation in the local market, higher operating costs in Colombia and lower sales to non-regulated clients in Peru," the company said in a statement.

Hydroelectric generation in the period fell 12 percent versus the previous year as the El Nino weather pattern reduced rains in Colombia.

Endesa is a unit of Chile-based regional energy group Enersis ENE.SN (ENI.N), which reported separately that its net profit fell 45 percent in the first half of 2010 versus last year. [ID:nN27109378]

"We remain quite calm about the results. Their explanation is entirely clear, which is the lower rates for the generation business in Chile," said Sergio Zapata, an energy sector analyst with Banchile Inversiones in Santiago.

Endesa's share prices were up slightly after the announcement, gaining about 1 percent from their Monday close and nearly 6 percent from the beginning of last week. ($1 = 543.09 Chilean pesos at the end of June) (Reporting by Santiago newsroom; Writing by Brad Haynes; editing by Leslie Gevirtz)