* Production down 0.5 pct m/m, up 1.1 pct y/y * Only highly volatile energy sector growing in Sept m/m * Output in Germany, France down, Portugal plummets By Martin Santa BRUSSELS, Nov 13 (Reuters) - Euro zone factory output fell more than expected in September against August as production in all but the energy sector fell, but it was still higher than in the same period of last year, in a sign the recovery was fragile but there. Industrial production in the 17 countries using the single currency dropped 0.5 percent on the month, following a 1.0 percent rise in August, data from the EU's statistics office Eurostat showed on Wednesday. Analysts polled by Reuters had expected a 0.3 percent fall. But the output in year-on-year terms rose 1.1 percent in September after an upwardly revised 1.1 percent fall in August, showing its strongest jump in two years, although from a low base, because in September 2012 it fell 2.7 percent. Production of durable consumer goods, such as cars and electronics, was down by 2.6 percent on the month in September, while the highly volatile energy output rose by 1.3 percent after a 0.6 percent drop in August, data showed. Production in Europe's two biggest economies, Germany and France, fell in September, while Italy returned to growth after two months of consecutive declines and Spain's output grew for a third month in a row. Germany, France, and Italy account for two-thirds of the euro zone's industrial output. The worst reading from among all euro zone countries was in Portugal, where production plummeted 11.2 percent on the month after a 8.0 percent increase in August. The 9.5 trillion euro economy crawled out of a 18-month-long recession in the second quarter with a 0.3 percent quarterly rise in GDP and economists expect it will continue to expand in third quarter, on which data due on Thursday.