Bifacial vs Monofacial Solar Panels: Is the Rear-Side Gain Worth It?
Monofacial panels generate from the front only. Bifacial panels add a glass rear that captures reflected light, but the extra yield depends entirely on how they are mounted. This page focuses on the head-to-head decision — for the full technology explainer see our bifacial solar panels guide and the broader solar panel types overview.
Quick Answer
For a typical Irish pitched roof with panels mounted close to dark tiles, bifacial rear gain is usually only around 2–5%, so it rarely justifies a premium on its own. Bifacial pays off on ground mounts, flat roofs with reflective membranes, and elevated agri or canopy installs, where rear gain can reach 8–30%. Many Tier 1 panels are now bifacial by default anyway.
What Is the Difference Between Bifacial and Monofacial Panels?
A monofacial panel has an opaque backsheet and generates electricity from its front face only. It is the standard, long-established construction and still accounts for the majority of residential installs. A bifacial panel replaces the backsheet with a second sheet of glass (a glass-glass build) so the rear cells can also produce power from light that reflects off the surface beneath and around the array.
The light bouncing onto the rear is called albedo. A bright white gravel or membrane surface reflects a lot of it; dark roof tiles or grass reflect very little. That single factor — what sits behind the panel and how far the panel is from it — is what decides whether bifacial is worth paying for. The cells and front-side output of a good bifacial panel are otherwise comparable to an equivalent monofacial module.
Bifacial is a construction choice rather than a separate cell chemistry. You will find it across many modern panel and cell types, and it is increasingly the default for ground-based and ground-mounted solar projects.
Bifacial vs Monofacial: Side-by-Side Comparison
The table below compares the two constructions across the factors that matter most when deciding for an Irish install: how they generate, typical extra yield, cost, durability, and the situations each suits best.
| Feature | Monofacial | Bifacial |
|---|---|---|
| Construction | Opaque backsheet, glass front | Glass-glass, dual-sided cells |
| Generates from | Front face only | Front face plus reflected rear light |
| Typical rear gain | None | Around 2–5% (close roof) to 15–30% (elevated, reflective) |
| Cost | Baseline | Around 5–15% premium (often none on Tier 1 ranges) |
| Durability | Standard | Glass-glass is typically more resistant to moisture and UV |
| Best for | Close-to-roof pitched residential | Ground mounts, flat roofs, canopies, agri |
| Weight | Lighter | Heavier (second glass sheet) |
How Much Extra Power Does Bifacial Actually Add?
The rear-side gain is not a fixed number. It depends almost entirely on the mounting and the surface beneath the array. These are typical ranges — your real figure depends on the specific site.
Standard pitched roof, dark tiles, panels close to roof
Around 2–5%
The rear sits close to a dark, low-reflectance surface with little gap for light to reach it. This describes most Irish residential installs, where the bonus is small.
Typical ground mount over grass or gravel
Around 8–12%
Panels are elevated with an air gap behind them, so reflected and diffuse light reaches the rear cells. A meaningful, repeatable uplift.
Light or reflective surface with elevation
Around 15–30%
White membrane flat roofs, pale gravel, or snow with the array raised well off the surface. This is where bifacial earns its keep.
Note that many current Tier 1 panels — such as the Jinko Tiger Neo, JA Solar DeepBlue, and Trina Vertex S+ ranges — are already bifacial by design. In those cases there may be little or no separate premium to pay, so the question becomes whether your mounting lets you capture any rear gain at all, rather than whether to spend more.
Are Bifacial Panels Worth It in Ireland?
For the most common Irish setup — panels mounted close to a dark pitched roof — the rear gain is limited, typically around 2–5%. That alone rarely justifies paying a premium. Where bifacial makes sense here is on ground mounts, flat commercial or domestic roofs finished with a reflective membrane, and agricultural or canopy structures where panels are elevated with clear space behind them.
Ireland's climate is a partial counterpoint. A large share of our annual light is diffuse rather than direct, and bifacial cells still respond to that scattered low-angle light. It does not turn a close-to-roof install into a strong performer, but on a well-elevated array the diffuse conditions are not the obstacle some assume.
On grants and tax, the construction makes no difference to what you can claim. The SEAI grant on the solar PV portion of a domestic install is capped at €1,800 and applies whether the panels are bifacial or monofacial. Domestic solar also benefits from the 0% VAT rate on supply and installation. Choosing bifacial does not add or remove either support.
Export is handled the same way too. Whatever the panel type, surplus electricity you send to the grid is metered by ESB Networks and paid for under the Clean Export Guarantee (CEG) by your electricity supplier. The decision between bifacial and monofacial is purely about generation economics at your specific site, not about eligibility for any Irish scheme.
Frequently Asked Questions
Are bifacial panels worth it for a typical Irish house roof?
Usually not on their own. On a standard pitched roof with dark tiles and panels mounted close to the surface, rear gain is typically only around 2-5%, which rarely justifies a premium. They make far more sense on ground mounts, reflective flat roofs, or elevated installs.
How much more do bifacial panels cost than monofacial?
Where there is a separate premium, it is typically around 5-15% over an equivalent monofacial module. However, many Tier 1 panels such as Jinko Tiger Neo, JA DeepBlue, and Trina Vertex S+ are already bifacial by design, so there is often little or no extra cost.
Do bifacial panels work in Ireland's cloudy climate?
Bifacial cells respond to diffuse, scattered light, which makes up a large share of Ireland's annual sunlight, so the climate is not a barrier in itself. The bigger factor is mounting: rear gain only materialises when panels are elevated above a reflective surface.
Does choosing bifacial change my SEAI grant or VAT?
No. The SEAI grant on the solar PV portion of a domestic install is capped at 1,800 euro and applies regardless of panel construction, and the 0% VAT rate on domestic solar applies either way. Panel type has no effect on eligibility.
Are bifacial panels more durable than monofacial?
Generally yes. The glass-glass construction used for bifacial panels is typically more resistant to moisture ingress and UV degradation than a traditional backsheet, though it also makes the panel heavier, which matters for roof loading.
Related Guides
Bifacial Solar Panels
How they work, output gain, cost, and whether they are worth it in Ireland.
Panel Types
Mono, poly, bifacial, TOPCon, HJT, IBC and more compared.
PERC vs TOPCon vs HJT
Solar cell technologies compared for Irish conditions.
Ground Mounted Solar Panels
Costs, planning permission, pros & cons vs roof-mounted, and space requirements.
Sources
- SEAI — Solar Electricity Grant — seai.ie
- NREL — Bifacial Photovoltaics Research — nrel.gov
- PVsyst — Bifacial System Modelling — pvsyst.com
Last updated: June 2026
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
John Rooney is the founder of Solar Info and has been covering the Irish solar energy market since 2023. He fact-checks all content against official SEAI data and maintains relationships with SEAI-registered installers across Ireland.
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