The fossil fuels used to transport that waste, experts say, is not typically considered in calculating solar's carbon footprint, giving scientists and consumers who use the measurement to gauge a product's impact on global warming the impression that solar is cleaner than it is.

NPR: Solar Industry Grapples With Hazardous Wastes

According to scientists who conduct so-called "life cycle analysis" for solar, the transport of waste is not currently being factored into the carbon footprint score, which measures the amount of greenhouse gases produced when making a product.

NPR: Solar Industry Grapples With Hazardous Wastes

This new edition of the guide the 17th since the first version was released in 2006 adds new criteria to evaluate companies based on their carbon footprint, use of renewable energy, sourcing of paper fiber and conflict minerals, and product life cycle analysis.

FORBES: How Green Are Your Gadgets?