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- Bifacial panels produce extra power from light reflected onto their back side.
- Gains range from near zero to around 10-15%, depending on what is behind and below the panel.
- Vertical mounting over a light surface (white floor, snow, gravel) helps; a panel flat against a wall gains almost nothing.
- The price premium is small, so they are rarely a bad choice, but don’t pay much extra.
Many balcony kits advertise bifacial panels with claims of 10-30% extra yield. The technology is real, but the number depends heavily on your setup.
In this article
How bifacial panels work
A standard panel has an opaque back sheet. A bifacial panel uses glass or a transparent back, so the rear of the cells can capture light that bounces off the ground, walls or floor. The rear side typically has 70-80% of the front side’s sensitivity (“bifaciality”).
When they help on a balcony
| Setup | Realistic extra yield |
|---|---|
| Panel mounted flush on a wall or solid railing | ~0% |
| Vertical on an open railing, dark floor below | 2-5% |
| Vertical, open railing, light-colored floor or wall behind | 5-10% |
| Raised ground mount over white gravel or snow | 10-15%+ |
These are typical ranges from field studies; your result depends on the gap behind the panel and surface reflectivity.
Special case: vertical east-west
A vertical bifacial panel facing east-west produces from the front in the morning and the back in the afternoon. This is used in agriculture. On a balcony it only works if both sides are open to the sky, which is rare.
Downsides
- Glass-glass bifacial panels are heavy, often heavier than standard panels of the same wattage.
- Rear mounting hardware can shade the back side.
- Some are more expensive.
Our advice
If a bifacial panel costs the same or only slightly more, take it, as long as the weight suits your mount. If the premium is significant, spend it on better placement instead: avoiding shade is worth far more. How shade affects output.
Bottom line
Treat bifacial gain as a small bonus, not a reason to buy. Weight, certification, warranty and fit on your balcony matter more. Our kit shortlist.
A quick way to estimate your own bifacial gain
Field studies summarized by the IEA’s photovoltaic program and by the U.S. national laboratory formerly known as NREL agree on the two things that matter: how much light the surface behind or below the panel reflects (its albedo) and how much open space there is behind the panel. You can judge both on your balcony in a minute.
| Surface behind or below | Typical reflectivity | What it means for the rear side |
|---|---|---|
| Dark tiles, asphalt, dark decking | Low (roughly 5-15%) | Little light reaches the back; expect a few percent at most |
| Grass, concrete, grey stone | Moderate (roughly 15-30%) | Small but real gain if the panel is raised |
| White gravel, white wall, light render | High (roughly 40-60%+) | The best case for a balcony or garden |
| Fresh snow | Very high | Big gains on winter days, but only while the snow lasts |
Reflectivity ranges are typical values used in solar modeling; your surface may differ.
Then check the gap. A panel clamped a few centimeters in front of a solid wall barely sees any rear light, whatever the wall’s color. A panel on an open railing with the balcony floor behind it, or a ground stand raised half a meter above gravel, gives the back side a real view of the sky and the ground.
Worked example
An 800 W kit on a south-facing open railing in Denver produces around 920 kWh a year with standard panels (see yearly production by city). With bifacial panels over light concrete, a 5% gain adds about 45 kWh. At 17 cents per kWh and 75% self-use, that is roughly $6 a year. Over 20 years it adds up to about $120, which is why a small premium can be fine but a large one rarely pays.
Weight is the other trade-off. Glass-glass bifacial panels of 400-450 W often weigh 22-25 kg (48-55 lb), more than many balcony railings were designed to carry in wind. If your mount or landlord limits weight, a lighter mono-facial panel is the safer choice. See no-drill mounts and wind-proofing.
Frequently asked questions
Do bifacial panels need special inverters?
No. They connect like any panel. The extra rear-side current is usually small enough to stay within inverter limits, but check the datasheet’s bifacial gain figures.
Are glass-glass panels more durable?
Glass-glass construction is often very durable and can carry longer warranties, but it is heavier. Make sure your mounting and railing can carry it.
Does painting the wall behind the panel white help?
It can add a few percent for a bifacial panel with enough gap behind it. Check with your landlord before painting anything.
Sources
- Bifacial photovoltaic modules and systems: experience and results (Task 13), IEA PVPS.
- Understanding bifacial photovoltaics potential: field performance, NREL / National Laboratory of the Rockies.
- Comprehensive study on the efficiency of vertical bifacial PV systems: a UK case study, Scientific Reports.
Sources checked in September 2026. Laws, prices and product details change; if you spot something out of date, tell us.