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Putting solar panels on a pergola? Bifacial panels could be a perfect fit.

Andrew Blok is an associate editor at CNET covering HVAC and home energy, with a focus on solar. As an environmental journalist, he navigates the changing energy landscape to help people make smart energy decisions. He's a graduate of the Knight Center for Environmental Journalism at Michigan State and wrote for several publications in the Great Lakes region, including Great Lakes Now and Environmental Health News. You can find him in western Michigan watching birds.

On its face, the concept behind bifacial solar panels is a bit counterintuitive. Unlike typical solar panels, which convert sunlight to electricity on just one side of the panel, bifacial panels generate electricity on both, even though the back faces away from the sun.

To take advantage of their two-faced design, bifacial panels need space behind them to allow reflected light to reach the panel. While it doesn't make sense to install bifacial panels right against a roof, for some home installations they could significantly increase the amount of energy an array can produce.

Sunlight reflects, to varying degrees, off of everything. If you've ever been outside after dark when there's snow on the ground, you've probably noticed how much lighter it is than without snow. This effect even has climate change implications. Research shows that ice reflects about 85% of sunlight, but open water reflects only 7%. As Arctic ice melts, the water underneath absorbs more light (and heat).

All this to say, there's enough light bouncing around to generate electricity on the back side of the panel too. To take full advantage of bifacial panels, there are a couple key considerations.

First, the more reflective the environment around the panels, the more energy they'll generate. A lighter colored environment will reflect more light and boost performance. "We're seeing that as the grass turns brown, it gets more reflective, and snow cover is great," one researcher said in a report from the National Renewable Energy Laboratory. It also means that desert countries, like Australia, with lots of reflective sand adopt bifacial panels quicker than their neighbors, the consulting firm Wood Mackenzie reported.

Second, there needs to be space for reflected light to reach the back of the panel. This means bifacial panels don't make sense for rooftops where they'll sit almost right against the shingles. They're best utilized in large, commercial installations where they're up in the air on poles, with plenty of space for light to reflect against the back. 

Bifacial panels outperform traditional, one-faced panels throughout the year. Under ideal conditions, bifacial panels can produce 27% more energy.

Bifacial panels don't cost much more than other solar panel options, so they're attractive options if you have a suitable place for them. Even though there's no benefit to installing them on a roof, homeowners might opt for bifacial panels in a few instances.

If your solar panels are mounted on the ground instead of a roof, bifacial panels could be a good choice. This is especially the case if you live in a snowy area or can install them over a more reflective surface, like sand.

Bifacial panels can also be beneficial if they're being used to build a covering over an outside area. A pergola or awning with an open space underneath will be far enough from the ground to allow reflected light to reach the back of the panel. Creative folks will likely find other ways to deploy bifacial panels.

Despite being unhelpful in most residential applications, bifacial panels are one more tool that could help you squeeze a bit more energy out of the sun. Using them in the right situation can help you achieve your energy goals for just a small premium.