Bifacial Solar Panels: How Much Extra Power You Really Get, What They Cost and When They Are Worth It

Bifacial solar panels collect light on both faces. The front works like any other module, and the rear picks up light reflected from the ground, a roof membrane or nearby surfaces. Many current N-type modules are bifacial, so the real question is how much the rear side will add on your site and whether that is worth the weight, price and design details.

What are bifacial solar panels?

A conventional (monofacial) panel has an opaque white or black backsheet, so only the front generates power. Bifacial solar panels replace that backsheet with a second sheet of glass (glass-glass) or a transparent backsheet, and use cells that can convert light arriving from the back as well. Modern N-type TOPCon and heterojunction cells are naturally suited to this, which is why so many current high-wattage modules are bifacial by default.

The rear side is less efficient than the front. Manufacturers express this as the bifaciality factor, the ratio of rear-side to front-side efficiency. The PVWatts Version 8 documentation from NREL (now NLR) describes it as “typically a value between 0.65 and 0.9” and tells users to take it from the module datasheet.

How do bifacial solar panels work?

The rear side runs on reflected and diffuse light, so its output depends on three things:

• Albedo (ground reflectivity). The Sandia PV Performance Modeling Collaborative lists typical values from PVsyst guidance: dry asphalt 0.09–0.15, grass 0.15–0.25, concrete 0.25–0.35 and fresh snow 0.82. Light surfaces bounce several times more light than dark ones.
• Height and spacing. A module mounted a few inches above a roof sees mostly its own shadow. Raised modules with open space beneath and between rows see far more reflected light.
• What sits behind the module. Rails, torque tubes, junction boxes and nearby rows shade the rear side unevenly.

Array size matters too. A 2017 study by NREL, Sandia and the University of Iowa found that in large arrays the middle module can produce up to 7% less energy than a single isolated bifacial module at 21% albedo, because the rows shade the ground beneath one another. A single test panel overstates what a full array delivers.

How much extra energy does the rear side really add?

Some of the best-documented US field data comes from NREL and Sandia. In a 2019 paper in the IEEE Journal of Photovoltaics, researchers compared bifacial and monofacial systems on single-axis trackers in Albuquerque, New Mexico, and eastern Oregon. Bifacial modules raised energy yield by 4% to 15% depending on module type and albedo, with a global modeled average of 9%. The Oregon bifacial system ran a performance ratio 9.4% higher than its monofacial twin. The same study warned that a center-mounted torque tube can cut rear irradiance by up to 20%.

Treat 5% to 10% as a realistic planning range for a well-designed ground or tracker system on ordinary ground, and anything above that as something your site has to earn with high albedo, height and clean rear-side geometry. Headline claims of much larger gains usually describe ideal conditions, such as snow cover or a single raised test module, not a typical install.

Bifacial vs monofacial solar panels

The practical conclusion: where the rear side can see light, a bifacial module adds real energy. Where it cannot, it behaves like a heavier monofacial panel.

Where bifacial panels are worth it

• Ground mounts and trackers. The rear side has open sky, room beneath and, ideally, light gravel or dry grass below. This is where the NREL tracker results come from.
• Flat commercial roofs. A white membrane reflects far more light than asphalt, and tilted rows on ballasted racking leave space for it to reach the rear side.
• Carports and pergolas. High mounting and light concrete below both help.
• Snowy regions. Fresh snow is one of the most reflective surfaces listed in the PVsyst guidance, and rear-side generation can help in winter.

Bifacial solar panels on roof: when they make little sense

Bifacial solar panels on roof installations are common simply because many modules are bifacial by default. On a typical pitched residential roof, flush-mounted a few inches above dark shingles, the rear sees a narrow, shaded gap over a surface with low reflectivity. The gain is small, so judge the module on front-side power, price, warranty and weight, and treat any rear-side contribution as a bonus. When reviewing an installer’s offer, ask how the production estimate treats the rear side. Our guide on what a home solar proposal should explain before you sign covers how to check those assumptions.

Weight is also a roof question. The 144-cell bifacial modules in the table below weigh about 70 lb each, so confirm that your racking and roof structure are rated for them.

Vertical bifacial solar panels

Vertical bifacial solar panels stand upright like a fence, usually facing east and west, so each face catches the sun in turn. They are used on farms, along fences and in snowy areas where snow does not settle on a vertical face.

The research is nuanced. A Sandia field report (2016) from the New Mexico Regional Test Center measured bifacial gains of 18% to 136% over monofacial modules in the same orientations, with the largest gain on vertical west-facing modules. Those are six months of data from one small 9.6 kW test array, and the largest figure compares vertical bifacial with vertical monofacial modules. The report did find that the vertical west-facing bifacial modules out-produced monofacial modules at every orientation tested, so treat it as a promising early result, not a planning number. A 2018 modeling study by the University of Iowa, NREL and Sandia found that without obstructions, tilted south-facing bifacial modules outproduce vertical east-west ones at most locations, but obstructions to the south can reverse that, especially at higher latitudes. Vertical systems mainly shift output toward morning and late afternoon; whether they beat a tilted array over a year depends on the site.

Worked example: what 5%, 10% and 15% rear gain means

Assumptions for illustration only: a ground mount of 20 bifacial panels at 600 W each, and front-side production of 1,400 kWh per kW per year. Your own figure depends on location, tilt and shading. You can estimate it for free with PVWatts, which supports bifacial modules and albedo inputs.

• Array size: 20 × 600 W = 12,000 W = 12 kW
• Front-side production: 12 kW × 1,400 kWh/kW = 16,800 kWh per year

Suppose a bifacial module costs $0.05 per watt more than a comparable monofacial one. The premium for this array is then 12,000 W × $0.05 = $600. At a 10% gain, $600 ÷ $252 per year is about 2.4 years to recover the premium (ignoring degradation and rate changes). If the price difference is zero, any rear-side gain is free energy. The electricity price of $0.15/kWh is an assumption, so replace it with your own rate.

Mounting, racking and inverter sizing

• Height. Raise the lower module edge well above the surface, within racking and code limits.
• Rear shading. Choose rails and clamps that keep the cell area at the back clear where possible. On trackers, ask how the torque tube is accounted for in the model.
• Clamping. Glass-glass modules usually specify allowed clamping zones and load ratings. Follow the installation manual exactly.
• Inverter and string sizing. Rear gain raises current and power above the front-side rating. Many datasheets include a table of output at several rear-gain levels, for example 5%, 15% and 25%. Your installer should size the inverter, conductors and fusing using the manufacturer’s bifacial ratings, and expect more clipping on a tightly sized inverter.

Bifacial solar panels for sale: real listing examples

The table below uses a snapshot of A1 SolarStore listings checked on October 12, 2026. Prices change often and several items showed limited stock, so treat this as an example of current pricing, not a quote. Per-watt values are the listing price divided by rated watts.

The large 144-cell modules such as the JA Solar 600 W assembled in the USA and the Phono Solar 590 W suit ground mounts and commercial rows, while the lighter 108-cell modules fit residential roofs where the rear side is a bonus. For a full ground array, buying a full pallet can lower the price per watt. See our guide to solar panels by the pallet. You can compare more models in the A1 SolarStore solar panels catalog.

What to check on the datasheet

• Bifaciality factor (often written as bifaciality or bifacial coefficient, for example 80% ± 5%). Higher means more rear-side output for the same light.
• Rear-gain power table. Output, current and voltage at stated rear-gain levels, used for inverter and wire sizing.
• Construction. Glass-glass or transparent backsheet, glass thickness, frame and the resulting weight.
• Mechanical loads and clamping zones, separately for front and rear.
• Warranty. Product term, linear performance guarantee and who handles claims in the US. Our deep dive on solar warranties and backup power explains how to read these terms.
• Certifications required by your installer and local authority, such as UL 61730.

Disadvantages of bifacial solar panels

• Gains are site-dependent and hard to predict precisely, because ground reflectivity changes with surface, moisture and season.
• Heavier modules when built glass-glass, which matters for roofs and handling.
• More design work: height, row spacing, racking shadows and inverter sizing all need attention.
• Little benefit when flush-mounted over a dark roof.

So, are bifacial solar panels worth it?

For ground mounts, trackers, carports and tilted rows on light flat roofs, usually yes. Field research shows real gains there. For a flush-mounted home roof, choose the panel on price, front-side power, warranty and weight, and do not pay a premium for the rear side. The best bifacial solar panels for your project are the ones whose datasheet, weight and warranty fit the mounting you plan to build.

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