New report from WattTime and First Solar explores how two key factors can determine the emissions impact of solar projects

If you’ve ever been on either end of a real estate deal, you’ve probably heard this old saying: “location, location, location.” This potentially overused adage imparts some obvious but useful lessons. For example, if you’re a small business owner investing in a new store, buying in one part of town versus another can be a complete game changer for how much money you’re able to make and how many people your business can reach, even if the service you’re providing in either location is identical.

The same concept holds true for solar projects and potential avoided carbon emissions. In fact, our research has shown geographic location to be the most important factor in determining the emissions impact of a new  renewable energy project.

The idea is fairly simple: If you build a new solar farm in a region that’s already saturated with—and maybe even curtailing surplus—solar energy, it won’t reduce grid emissions nearly as much as a solar farm built in a region still mainly reliant on coal-fired electricity. What you displace matters, and our goal is to displace high-emissions electricity generators. At WattTime, we call this concept “emissionality,” and according to our research, using the practice of emissionality when siting new renewables projects can help us avoid up to 380 percent more greenhouse gas emissions.

While location is clearly the heavy hitter of solar project optimization, there are other aspects to factor into the equation. One that we’ve recently taken a closer look at, along with our partners at utility-scale solar company First Solar, is the idea of “embodied emissions.” Different types of solar generation hardware cause different quantities of carbon emissions during production, deployment, and over their lifespans. For example, silicon technologies—especially monocrystalline—result in a higher emissions impact because of more emissions-intensive material and manufacturing requirements. But thin film technologies have a much lower emissions impact throughout their lifespans. By calculating the amount of avoided emissions achieved through strategic siting minus the emissions created through the lifespan of the technology deployed, we’re able to consider the overall net emissions impact of various projects.

A new report from WattTime and First Solar explores the net emissions impact of four common solar PV technologies in three different regions of the world with vastly different grid mixes—France, North Carolina, and California—across a typical 25-year lifespan. Spoiler alert: all the systems we tested had a net emissions reduction impact over a period of 25 years, but some were much better than others. The most dramatic swings in avoided emissions, as expected, were found when solar projects were placed in fossil-fuel-heavy grids compared to cleaner grids. Projects in North Carolina—where the marginal power generator is usually coal or natural gas—displace nearly 15 times more emissions than projects in France, where marginal generators are usually low-carbon.

But when working in relatively clean grids, using solar technologies with lower lifecycle embodied emissions helped make a great thing into an even greater thing. If we look again at France, using cadmium telluride technology instead of monocrystalline amplified net emissions reductions by a factor of nearly three.

As more of our electricity grids make the gradual transition from fossil fuels to renewables, thinking strategically about what technologies we use and where we put them can help us meet carbon reduction goals on or ahead of schedule. For more takeaways, as well as a deep-dive into lifecycle analysis and the concept of displaced emissions, download the full report.