(IDEX Online) - China's production of lab grown diamonds is down by as much as 15 per cent as the country battles a desperate shortage of electricity.A reduction in output by the world's largest lab grown producer could bump up prices in the weeks before Christmas.China is responsible for around 3m carats a year of the 7m carats lab growns produced globally in a year.But the power-hungry industry has been hit by coal shortages as President Xi Jinping (pictured) tries to reduce greenhouse gas emissions.Liu Houxiang, a consultant at the National Gemstone Testing Center, told Bloomberg News output of jewelry-grade gems was down by 10 per cent to 15 per cent in October.