China's power consumption slowed sharply in July, adding to signs the world's second-largest economy may be losing steam.

Electricity consumption, a broad measure of economic vitality, rose 3 percent year on year to 509.7 billion kwh in July, slowing sharply from 5.9 percent growth seen in June, according to data from the National Energy Administration (NEA) on Thursday,

The weak demand in July also brought the growth rate of power consumption in the first seven months down to 4.9 percent, compared with 5.3 percent recorded in the January-June period, according to the NEA.

A string of economic data released earlier this week, including the drastic decline in new credit and weaker-than-expected investment figures, indicated that the Chinese economy might need more momentum to get back on track with strong growth.

During the January-July period, electricity use by the primary industry fell 2.1 percent from a year earlier, narrowing from a 4.6 percent decline in the first half of the year. Power consumption by the manufacturing sector rose 4.7 percent, compared with 5.1 percent seen in the first six months.

Power use by the service sector rose 6.5 percent to 375.4 billion kwh, slightly slower than the 6.9 percent recorded in the January-June period.

Growth of residential power use in the January-July period also slowed to 5.7 percent from 6.6 percent seen in the first half of the year.

As a result, more of the country's electricity generating devices were left idle as the average operational time of power plants dropped by 102 hours in the first seven months, widening from 79 hours recorded in the first half.

China's economic growth slowed to 7.4 percent year on year in the first half, according to data from the National Bureau of Statistics.