Many buyers assume a bifacial panel gives them a second full-power side, so a 400 W panel becomes 800 W. It does not. Bifacial solar panels collect sunlight on both the front and the back, but the extra output usually lands in the single digits, and it depends on rear-side light, ground reflectivity, panel height, spacing, and shading. Check those site conditions first, then decide if the gain is worth the cost.
Quick answer
Bifacial panels turn light hitting either side into electricity. Expect a modest gain, often 5% to 10% in good setups, not double power. They pay off when the back is exposed to light.
- Best for ground mounts, trackers, carports: open space under the panels
- Best for bright surfaces: white gravel, light roofing, snow
- Skip for flush, shaded roofs: the back sees little light
- Bifacial panels collect light on the front and back. The advertised wattage is the front-side rating only.
- Real gain depends on albedo (ground reflectivity), height, row spacing, and shading. NREL cites results around 6.5% to 9% in certain tracker setups.
- Close-mounted panels on an opaque roof usually see little rear light, so the benefit is small.
- Judge cost by extra installed cost divided by the value of extra yearly electricity, not by panel price alone.
- Bifacial panels generally work with the same inverters as standard panels.
- What Are Bifacial Solar Panels?
- How Are Bifacial Panels Different From Monofacial Panels?
- How Much Extra Electricity Do Bifacial Panels Produce?
- How Are Bifacial Solar Panels Rated?
- How Are Bifacial Solar Panels Mounted?
- Can Bifacial Solar Panels Be Used on a Roof?
- What Are Bifacial Solar Panels Used For?
- How Much Do Bifacial Solar Panels Cost?
- Why Are Bifacial Solar Panels Better, and When Are They Not?
- Installation, Cleaning, Snow, and Warranty
- What Should Buyers Check Before Choosing?
- Frequently Asked Questions
What Are Bifacial Solar Panels?
Bifacial solar panels, also called bifacial PV panels, are modules with photovoltaic cells that produce power from sunlight hitting the front and the rear. Direct sun hits the front. The back picks up light reflected from the ground, nearby surfaces, and the sky.
“Bifacial” simply means “two faces.” The cells are built to accept light from both sides. Most bifacial modules use glass on both sides (dual-glass) or a transparent backsheet, so light can reach the rear of the cells. A standard panel uses an opaque white or black backsheet that blocks it.
How Are Bifacial Panels Different From Monofacial Panels?
A monofacial panel produces power from the front only. A bifacial panel produces power from both sides, but only gains extra energy if the back receives light. Here is the side-by-side view:
| Feature | Monofacial | Bifacial |
|---|---|---|
| Active cell surfaces | Front only | Front and rear |
| Back of module | Usually opaque backsheet | Glass or transparent backsheet |
| Rear light needed? | No | Yes, to earn extra output |
| Typical mounting | Flush or low-profile roof | Raised ground mount, tracker, carport, open frame |
| Best applications | Close-mounted residential roofs | Ground arrays, carports, farms, utility sites |
| Cost consideration | Lower module price in many quotes | Module premium varies; racking may cost more |
| Likely gain conditions | Not applicable | High albedo, tall clearance, wide row spacing, little rear shading |
How Much Extra Electricity Do Bifacial Panels Produce?
Most well-designed systems gain roughly 5% to 10% over similar monofacial panels, and poor setups gain close to nothing. According to NREL, bifacial gain depends on site configuration and surface albedo. NREL cites results around 6.5% for PERC and 9% for silicon heterojunction systems in certain tracker configurations (NREL’s bifacial potential report).
What controls bifacial gain?
- Albedo: the share of light a surface reflects. White surfaces and snow raise rear light. Dark ground, vegetation, and dirt lower it.
- Clearance: more height lets more reflected light reach the back and spreads it more evenly.
- Row spacing: wider gaps between rows let more light reach the ground behind the panels.
- Orientation and tilt: these change how much sky and ground the rear “sees.”
- Shading: racking, wiring, and the junction box can shade the back. Uneven rear light also causes mismatch losses.
- Bifaciality: how well the rear side converts light compared with the front.
Worked example: a 400 W bifacial panel
These numbers are site-dependent. Change the assumptions to match your home.
- Front rating: 400 W (0.4 kW)
- Peak sun hours: 4.5 per day (typical US range is roughly 3 to 6)
- System losses: 14% (so 0.86 of nameplate output)
- Electricity price: $0.17 per kWh (near the national average from the U.S. Energy Information Administration)
Base production: 0.4 kW × 4.5 hours × 365 days × 0.86 = about 565 kWh per year.
| System-level bifacial gain | Annual output | Extra kWh | Extra value at $0.17 |
|---|---|---|---|
| 0% (flush roof, little rear light) | 565 kWh | 0 | $0 |
| 5% | 593 kWh | 28 kWh | about $4.80 per year |
| 10% | 622 kWh | 57 kWh | about $9.60 per year |
So one panel adds roughly $5 to $10 of electricity a year. At 40 cents per kWh, a high-price state, those figures more than double. At 12 cents, they shrink. The gain is real, but small per panel. It adds up across a large array.
How Are Bifacial Solar Panels Rated?
The headline wattage on a bifacial panel is normally the front-side rating under standard test conditions. Rear-side output is not added on top of it. It is estimated from the bifaciality factor and your site conditions.
The bifaciality factor is the ratio of rear-side performance to front-side performance, shown as a percentage. A module with 70% bifaciality converts rear light at about 70% of the front-side rate. Higher is better, but only if light reaches the back. Check the datasheet for these items:
- Front-side power in watts (the number you compare on price)
- Bifaciality factor
- Front-side efficiency
- Any listed rear-irradiance power figures. Some datasheets show output at added rear light levels, which are test scenarios, not guarantees.
A “550 W bifacial” panel is a 550 W front-rated panel. Treat any claim of “up to 30% more” as a best-case lab or site result, not a promise.
How Are Bifacial Solar Panels Mounted?
Bifacial panels are mounted on raised racking so the back can see reflected light. Common methods include:
- Fixed-tilt ground mounts: panels sit well above the ground at a set angle.
- Single-axis trackers: panels follow the sun, which raises both front and rear light. NREL’s tracker results show some of the stronger gains.
- Carports and canopies: light bounces up from pavement or the ground below.
- Agrivoltaic systems: raised panels over crops or grazing land, with space for light to pass through.
- Vertical or east-west fences: upright panels collect morning and evening sun on opposite sides.
Good racking keeps beams, rails, and wiring out of the way of the rear cells. Follow the manufacturer’s clamp-zone instructions, since glass-glass modules can be frameless or have different mounting requirements.
Can Bifacial Solar Panels Be Used on a Roof?
Yes, bifacial panels work on a roof, but they are often not a good reason to pay extra. A panel mounted close to an opaque roof gets little rear light, so the theoretical bifacial advantage is small. You get roughly front-side output only.
Some roof setups do better:
- Flat roofs with tilt-up racks: panels sit higher, and a white membrane roof reflects a lot of light.
- Raised or open structures: patio covers, pergolas, and translucent roofs let light pass.
- Snowy climates: snow is highly reflective, though it can also cover panels.
For a standard pitched shingle roof with flush mounting, a monofacial panel is usually the sensible choice. Any grid-tied roof or ground system needs a licensed electrician and a utility interconnection agreement. If you rent and are considering a small plug-in system, rules vary by state and change quickly, so confirm with your utility. Never use extension cords, and never bypass a microinverter’s grid shut-off.
- If the panels sit flush on a dark, opaque roof, choose monofacial unless the bifacial price is nearly identical.
- If panels are raised 2 feet or more above a bright surface with open space behind, bifacial is worth pricing.
- If the ground is dark, weedy, or shaded, expect a gain near the low end.
What Are Bifacial Solar Panels Used For?
Bifacial panels are used where the rear surface is exposed: utility-scale solar farms, trackers, commercial ground arrays, carports, agrivoltaic farms, and some flat-roof and residential ground-mount systems. They are common in large projects because small gains multiply across thousands of modules.
How Much Do Bifacial Solar Panels Cost?
Bifacial modules may cost somewhat more per watt than comparable monofacial ones, but prices change often and vary by brand, so compare current written quotes. Do not stop at module price. The number that matters is total installed system cost.
Bifacial modules generally use the same inverters and, in many systems, the same electrical architecture as monofacial modules (see NREL’s bifacial_radiance overview). The cost differences usually come from the modules and from racking that raises the panels.
A simple payback calculation
Divide the extra installed cost by the value of the extra yearly electricity.
Payback years = extra installed cost ÷ (extra kWh per year × price per kWh)
Using the worked example above, suppose the extra cost is $30 per panel. This figure is illustrative only. Use your own quote.
- At 10% gain ($9.60 per year): $30 ÷ $9.60 = about 3.1 years.
- At 5% gain ($4.80 per year): $30 ÷ $4.80 = about 6.3 years.
- At 0% gain (flush roof): it never pays back.
Why are bifacial solar panels cheaper?
They usually are not cheaper per panel. They can be cheaper per kWh over the system’s life, because the same hardware yields more energy. If a quote shows a bifacial panel at the same or lower price than a standard one, you get the extra option almost for free. Otherwise, run the payback math.
Why Are Bifacial Solar Panels Better, and When Are They Not?
Bifacial panels are better when they can use the light that standard panels waste. Many are also built with glass on both sides, which resists moisture and wear. Their advantages are extra energy, a better chance of lower lifetime cost per kWh, and a durable build.
They are not better when:
- The array sits flush on an opaque roof.
- The ground or surface is dark, weedy, or dirty.
- Rows are packed tightly or the rear is shaded.
- The added clearance needs costly or complex racking.
- The price premium is high compared with the likely gain.
Design tools that estimate gain
Installers and engineers model rear-side light with tools such as SAM, PVsyst, and the open-source bifacial_radiance. NREL’s work on these models, including field results from a 75 kW bifacial test, shows the results depend on getting inputs right, especially albedo and height. Ask your installer which tool they used and what albedo they assumed.
Installation, Cleaning, Snow, and Warranty
- Installation: glass-glass modules can be heavier, so confirm racking and structure can carry them. Handle edges carefully.
- Cleaning: dirt on the ground and on both glass surfaces cuts light. Make sure you can safely reach the panels.
- Snow: snow on the ground can add rear light. Snow on the panel blocks the front. Tilt and height affect how fast it slides off.
- Glare: light surfaces under panels can bounce light toward neighbors or windows. Check the layout.
- Warranty: read the product and performance warranty terms for the specific module, including how rear-side output is treated.
What Should Buyers Check Before Choosing?
Roof versus ground-mount checklist
| Check | Flush roof | Raised ground mount or carport |
|---|---|---|
| Panel clearance | A few inches. Little rear light. | Often 2 feet or more. Better rear light. |
| Reflective surface | Dark shingles reflect little | White gravel, light pavement, or snow help |
| Rear shading | Roof and rails block light | Watch rails, posts, and nearby buildings |
| Row spacing | Not an issue on single rows | Wider spacing raises rear light |
| Snow | Can slide or stick | Higher clearance helps shedding and reflection |
| Glare | Rarely a problem | Check neighbors and windows |
| Access for cleaning | Roof access and safety | Usually easier at ground level |
Datasheet and proposal checklist
- Is the wattage front-side only? (It normally is.)
- What is the bifaciality factor?
- What albedo and height does the installer’s model assume?
- What gain percentage does the proposal use, and what modeling tool produced it?
- What is the total installed cost difference compared with a monofacial design?
- Are the inverter and electrical parts the same?
- What are the product and performance warranty terms?
- Is a licensed electrician handling the wiring and interconnection?
Frequently Asked Questions
What are bifacial solar panels?
They are solar panels that generate electricity from sunlight on both the front and rear surfaces. The front gets direct sun. The back collects reflected light from the ground and surroundings.
What are bifacial PV panels?
“Bifacial PV panels” is another name for bifacial solar panels. PV stands for photovoltaic, meaning the cells convert light directly into electricity.
How are bifacial solar panels rated?
The advertised watts are normally the front-side rating. Rear-side performance is described by the bifaciality factor and is estimated with site modeling. It is not a second full-rated output.
How are bifacial solar panels mounted?
They are mounted on raised racking, such as ground mounts, trackers, carports, and open canopies, so the back can receive light. Racking should avoid shading the rear cells.
How much are bifacial solar panels?
Prices vary by brand and market and change often. Many bifacial modules cost somewhat more per watt than monofacial ones. Compare total installed cost, then use the payback formula: extra cost divided by the value of extra yearly electricity.
What are bifacial solar panels used for?
They are used on solar farms, trackers, ground arrays, carports, agrivoltaic sites, and some flat-roof systems, where the rear surface is exposed to reflected light.
Can bifacial solar panels be used on a roof?
Yes, but flush roof mounting gives little rear light, so the extra benefit is small. Raised flat-roof racks, reflective roofing, and open or translucent structures work better.
Why are bifacial solar panels better?
They can capture light that standard panels miss, which raises annual energy and can lower the lifetime cost per kWh. NREL research reports gains of roughly 4% to 7% can still improve levelized cost of energy under lower-performance conditions (see NREL’s report). They are not better on shaded, flush, dark-surface installs.
Why are bifacial solar panels cheaper?
Usually they are not cheaper per panel. They can be cheaper per kWh produced over time if rear-side gain is strong and the added cost is small. Run the payback calculation with your own quote.
Why bifacial solar panels?
Choose them when you have raised mounting, bright ground, and open space behind the panels. In those cases, they turn wasted reflected light into extra electricity with mostly the same inverter and electrical equipment.
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