Solar-grade polysilicon and finished photovoltaic panels accelerated their declines in the past week, according to EnergyTrend.com, raising concerns among investors about the recovery in demand for the products.

The price of polysilicon, the main raw material in solar generators, fell by 1.1 percent the past seven days to an average $50.52 per kilogram ($22.92 per pound) compared with a 0.8 percent decline last week, EnergyTrend said today in a report on its website. Solar panel prices fell 2.4 percent to $1.19 per watt compared with a 0.9 percent decline last week.

Investors are looking for the price of photovoltaic equipment to stabilize to bolster hopes for a recovery of demand in Germany where new installations slumped the first five months of the year. Polysilicon fell 35 percent from March to July as production increased faster than demand, according to a separate price index by Bloomberg New Energy Finance.

Demand is starting to rise “but it’s not strong yet,” said Charles Yonts, a solar analyst at CLSA in Hong Kong. “Two weeks from now if it’s still not clear, we’re in trouble.”

Renewable Energy Corp ASA (REC), the Sandvika, Norway-based polysilicon-maker, fell as much as 2.7 percent after this week’s pricing data was published and traded down 0.8 percent at 9.90 kroner at 12:37 p.m. today in Oslo. Wacker Chemie AG (WCH), the second-biggest polysilicon producer, fell as much as 1.4 percent after the news and traded down 3 percent at 98.36 euros.

Solarworld AG (SWV), the German panel maker struggling to compete with lower-cost Chinese rivals, fell as much as 2.6 percent and was 1.8 percent lower at 5.76 euros.