UPDATE 1-Eqecat sees Sandy insured losses up to $20 bln in U.S.

* Economic damages up to $50 bln

* Loss estimate is double prior forecast

Nov 1 (Reuters) - Disaster modeling company Eqecat now estimates that monster storm Sandy caused up to $20 billion in insured losses and $50 billion in economic losses in the United States, the company said on Thursday.

The insured loss estimate is double what Eqecat forecast previously. The firm said subway and electrical outages will produce much more substantial losses than had been expected.

At the high end of the range, Sandy would rank as the fourth-costliest catastrophe ever in the United States, according to the Insurance Information Institute, behind Hurricane Katrina, the 9/11 attacks and Hurricane Andrew.

Eqecat's estimate is higher than peer AIR Worldwide, which projected insured losses from Sandy at $7 billion to $15 billion. RMS, the other modeler used by the insurance industry to forecast losses, has said only that Sandy would clearly be costlier than last year's Hurricane Irene.