Just how green are the solar panels gracing your rooftop? For most home- and business-owners, it’s still difficult to tell—but, if rankings are your thing, the Silicon Valley Toxics Coalition’s 2010 Solar Company Survey and Scorecard may be a good starting point. Released earlier this week, the San Jose-based organization’s report surveyed 25 of the world’s biggest solar photovoltaic panel and/or cell manufacturers and scored them based on their environmental practices and policies, which included “Extended Producer Responsibility and Takeback” (product recycling), green jobs, chemical use and disclosure. German companies topped the list, with Q-Cells, Calyxo and SolarWorld in the lead, and American powerhouse First Solar trailing not too far behind.

If these results surprise you, it might be because, out of the 25 companies surveyed, only 14 responded—although these 14 represent a hefty 28% of the 2008 world solar module market share. (Companies that presumably did not respond include Sharp, SunPower, Suntech and Solyndra, who all received scores of 0.) Furthermore, the SVTC states on the Solar Scorecard website that “product takeback and recycling” is not a common feature of most solar companies, which may partly account for the low response rate as well as the mid-to-low scores the majority of respondents received. Other findings included:

Seven of the responding companies have “undertaken analysis of their supply chain to document the social and environmental impacts associated with different production phases.”

Six companies report that their products contain lead, the most commonly used toxic element/chemical of those reviewed. All of these companies have plans to phase out lead eventually, though most say that the timeline is undetermined. Two companies will begin phasing out lead in 2010. Six companies report that they have employees doing manual lead soldering.

Three companies (Abound Solar, First Solar, and Calyxo) have products that contain cadmium compounds, and that they do not have plans to phase them out. No responding companies use mercury, hexavalent chromium (Cr6+), polybrominated biphenyls (PBB), or polybrominated diphenyl ether (PBDE).

The Solar Scorecard touts itself as the first survey to assess and compare the environmental procedures and performance of solar companies, and, as far as we know, it is currently the only bearer of this title. As with any company manufacturing products for the benefit of the environment—or any large company in general—the corporate social responsibility aspect of solar manufacturers’ operations is more important than ever, and it’s heartening to see an industry watchdog emerge. While the SVTC’s pool of information is still smaller than ideal—and the “green” nature of its survey questions was occasionally dubious (for example, what does prison labor have to do with a company’s commitment to environmental protection?)—chances are the 2011 Solar Scorecard will see an improved response rate, as well as a lot more buzz.