UPDATE 1-Acciona 9-mth core earnings beat forecasts

* Core profit falls 4.8 percent but beats forecasts

* Better performance down to margin improvement - analyst

* New energy capacity offsets weak power prices

* Shares up 1.6 percent

(Adds detail, analyst quote)

MADRID, Nov 12 (Reuters) - Spanish construction and energy group Acciona (ANA.MC) beat analysts' forecasts for nine-month core earnings on Thursday, due to better than expected margins and new energy capacity.

Earnings before interest, taxes and other items (EBITDA) at its renewable energy division fell just 3.5 percent as new generation capacity offset steep falls in electricity pool prices during 2009.

"Results are better than expected thanks to an improvement in profit margins," Banesto said in a note to clients, higlighting a notable improvement at the group's infrastructure division, and new capacity at Acciona Energy.

Spanish power demand has recovered only partly from severe falls at the beginning of the year and is still down about 5 percent from a year earlier, while the drop in pool prices has been about 40 pct.