Skip to main content

When Will Solar Energy Be Clean?

A reminder that almost everything we do produces greenhouse gases, directly or indirectly (but solar’s still looking pretty good).

By Nathan Collins


(Photo by Pablo Blazquez Dominguez/Getty Images)

Is solar energy actually clean?

Sure, solar panels themselves don’t emit carbon dioxide or other greenhouse gases, but there are other things to consider. Indeed, a new report suggests solar may not have reached its carbon break-even point, where the carbon savings from solar panels equal the associated carbon emissions.

“Clean energy” is a relative term. Think of electric cars: The vehicles themselves don’t put any carbon into the atmosphere, of course, but there are other things to consider. For one, the electricity that powers those cars has come from somewhere, and, in some places, that means burning coal. There’s also the energy used to build the car, and the energy—probably in the form of diesel—used to transport it to a dealer.

Solar energy has the same basic problem, Atse Louwen, Wilfried G.J.H.M. van Sark, and their colleagues write today in Nature Communications. “Since the 1970s, installed solar photovoltaic capacity has grown tremendously [but] rapid growth has led to concerns regarding the energy consumption and greenhouse gas emissions of photovoltaics production,” they write.

The carbon savings from solar electricity have most likely already made up for the costs associated with developing and deploying it.

The question is, do the benefits outweigh costs?The solar cell industry was a net consumer of electricity until as recently as 2010, according to a 2013 study—that is, up to that point the industry had used more electricity to make solar cells than those cells had managed to produce.

But that’s electricity use, not greenhouse gases. For that, Louwen and his team gathered 40 life-cycle assessments of solar electricity-generating systems, conducted between 1976 and 2014. Each of those assessments attempts to account for all the greenhouse gases emitted during the production and installation of solar cells, as well as how much energy solar cells produce—and, therefore, how much less carbon is emitted when switching from fossil fuels.

As the solar industry has expanded, the researchers found, greenhouse gas emissions have dropped enormously: As a function of the total energy a solar cell produces over its lifetime, carbon dioxide and carbon dioxide equivalents have dropped by between 86 and 95 percent since the late 1980s and early ’90s, depending on the type of solar cell. Each time solar capacity doubles, the team estimates greenhouse gas emissions per solar panel decline between 17 and 24 percent.

Based on that data and projections of future solar expansion, the team estimates that the carbon savings from solar electricity have most likely already made up for the costs associated with developing and deploying it—but, even in the worst case, in which the technology advances relatively slowly, the break-even point should arrive by about 2018.