It is a fact that solar panels, unlike fossil fuels, emit no carbon dioxide or any other greenhouse gas. However, the issue with solar panels is found in the way they are manufactured.

It takes a lot of energy to create a solar panel. Solar panels implement silicon, which they use to capture and transfer heat from the sun. Silicon is used because of its relatively high melting point which keeps the solar panel functional in extreme heat. The silicone must be melted in the manufacturing process of the solar panels, however, and this process uses electricity, more often than not electricity produced by burning fossil fuels.

Environmentalists refer to the initial amount of electricity used in creating a solar panel as a “carbon debt.” This debt has to be paid back before the solar panel is producing truly clean energy. For instance, if it took 1000 watts of electricity to create a solar panel, then that solar panel will have to produce 1000 watts of electricity to break even.

A scientist from Utrecht University in the Netherlands, Wilfried van Sark, has studied the carbon footprint created in the manufacturing of solar panels between 1975 and 2015, something no previous study into the matter has taken into account.

Using data from the International Energy Agency, Dr. Van Sark was able to estimate the number of solar panels installed throughout the world in this time frame. This data also revealed that the amount of energy used to produce solar panels varies according to where they are manufactured. More technologically advanced nations are able to make solar panels with a lower energy cost.

Dr. Van Sark concluded that the solar panel systems created in 1975 produced around 400 grams of carbon dioxide per kilowatt-hour of energy they were able to produce in the panel’s lifetime. The solar panels of 2015 produce only 20 grams.

While these numbers show that progress has definitely been made over the decades, the process by which solar panels are made still produces greenhouse gases. It does appear, however, that the act of making solar panels becomes more efficient over time, meaning less electricity is used. Dr. Van Sark estimates that every time the solar capacity of the world is doubled, the amount of energy required to make the solar panels is reduced by around 12%. This offers an optimistic outlook that soon solar panels will be made with tiny amounts of energy, making them even more effective in combatting greenhouse gases.