China's power consumption stood at 269.85 billion kilowatt hours (kwh) last month, down 3.7 percent compared with October last year, the first year-on-year monthly decrease since 1999.

According to the China Electricity Council (CEC), electricity consumption was 2.9 trillion kwh in the first 10 months, up 8.27 percent from the same period last year, compared with 9.67 percent in the first nine months.

Power supply also dropped last month with total electricity generated at 264.5 billion kwh, down 4 percent from October last year.

"Power generation was dragged down mainly by a 5.2 percent year-on-year decrease in coal-fired power supply, which accounts for about 80 percent of China's total power," the CEC statement said.

Analysts with Shanghai-based Guotai Jun'an Securities said the drop in consumption and supply signaled a slowdown in the country's economy that went "beyond expectations".

"The sudden slowdown in power demand shows many companies in the manufacturing sector have cut production due to a continuous price slump of industrial commodities both at home and abroad," said a Guotai Jun'an analysis issued on Friday.

Experts further warned the decrease in power supply may sound an alarm for future economic slowdown, as successive falls in power generation often precede a similar downward trend in economic growth.