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What: Shares of solar panel maker Yingli Green Energy (NYSE: YGE) are getting rained on today, plunging by as much as 10%, as fellow solar company Canadian Solar (Nasdaq: CSIQ) said its gross margin will come in worse than expected.

So what: The comments have sparked a sell-off within the solar sector, including names like Suntech Power (NYSE: STP) and also stateside counterparts like First Solar (Nasdaq: FSLR). Canadian Solar said its gross profit margin would likely be in the range of 2%-5%, compared to the previous guidance of 9%-12%.

Now what: Management attributed weak demand to customers waiting as long as possible before committing to purchases, which in turn is due to declining prices. Subsidies from important solar-using countries like Germany and Italy have been drying up, and the sector is plagued by oversupply, adding downward pressure on average selling prices. Solar stocks tend to move in lockstep with each other, and the recent cloudiness in the sector isn’t making it easy.

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Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. The Motley Fool owns shares of First Solar. Motley Fool newsletter services have recommended buying shares of First Solar. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.