Monocrystalline vs polycrystalline vs bifacial solar panels
What the three terms mean, why the choice has narrowed, and which numbers on the datasheet tell you whether a panel suits your roof.
Monocrystalline and polycrystalline describe the silicon a panel's cells are made from; bifacial means the panel can also collect light through its back. They are not three rival options: a panel can be monocrystalline and bifacial at the same time. Monocrystalline panels produce more power per square metre, and none of the four manufacturer datasheets we compare below uses polycrystalline cells. So on a UK quote, the useful comparison is between specific models: power for the roof space you have, behaviour in heat, weight, warranties and the price of the whole system.
What is the difference between monocrystalline and polycrystalline?
The difference is in how the silicon for the cell is made. In a monocrystalline cell the silicon is a single crystal: the cells look uniform and dark, and they produce more power from the same area. In a polycrystalline cell the silicon is cast from many crystals: the process used to be cheaper, the cells have a blue, speckled look, and they produce less power per square metre.
For years that was a trade-off between price and output. None of the four example panels in the table below is polycrystalline, so the table compares differences between today's higher-efficiency cell designs. If a quote still offers a polycrystalline panel, that is not a fault in itself, but the choice should be justified by a lower price for the whole system per kWp of capacity, not by the cell type.
My yearly electricity use is
Your yearly electricity use helps us size your solar panel system.
How to read the jargon, with four panels compared
N-type describes the kind of silicon used in the cell. TOPCon is a cell design that helps limit electrical losses. ABC (All Back Contact) is AIKO's name for cells with their electrical contacts on the back, and HPBC is LONGi's name for its back-contact cell. These terms describe how the cell is built; what they do for your roof shows up in the efficiency, temperature and warranty figures. Pmax is the panel's maximum rated power.
| Panel (datasheet edition) | Cell | Glass | Max efficiency | Max power | Pmax temperature coefficient | Weight | Size |
|---|---|---|---|---|---|---|---|
| Trina Vertex S+ NEG9R.28 (TSM_EN_2026_A) | N-type i-TOPCon, 144 cells | dual glass, 1.6 mm + 1.6 mm | 23.8% | 475 W (0/+5 W) | −0.29%/°C | 21.0 kg | 1,762 × 1,134 × 30 mm |
| JinkoSolar Tiger Neo 54HL4R-B (F1.3-EN) | N-type monocrystalline, 108 cells | 3.2 mm front glass, anti-reflective | 22.02% (440 W version) | 440 W | −0.29%/°C | 22 kg | 1,762 × 1,134 × 30 mm |
| LONGi Hi-MO X6 Scientist LR5-54HTH (V19) | HPBC back-contact, 108 cells | single glass, 3.2 mm | 23.3% | 455 W (0 to 3%) | −0.290%/°C | 20.8 kg | 1,722 × 1,134 × 30 mm |
| AIKO Neostar 2P AIKO-A-MAH54Mw (V4.1) | N-type ABC, 108 cells | 3.2 mm tempered glass | 24.3% | 485 W | −0.26%/°C | 20.6 kg (±3%) | 1,757 × 1,134 × 30 mm |
The figures are for the models and datasheet editions named, not for each brand's whole range. These are the manufacturers' international datasheets; the panel in your quote may be a different power version or edition, so check its exact model code against its own datasheet.
Temperature coefficient: how a panel copes with heat
The temperature coefficient of power tells you how much output the panel loses for every degree its cells run above the 25 °C test condition. The closer the number is to zero, the better the panel copes with heat. Of the four, three are at −0.29%/°C and the ABC panel is at −0.26%/°C.
It matters in the UK too, because the cells run much hotter than the air. Three of the datasheets give a nominal operating cell temperature of 43 to 45 °C in 20 °C air, with 800 W/m² of sunshine and a light breeze (1 m/s). As an illustration, cells at 45 °C are 20 °C above the test condition: a −0.29%/°C panel loses about 5.8% of its rated power from heat alone at that moment, and a −0.26%/°C panel about 5.2%. That is a snapshot on a warm, sunny moment, not an annual loss. Across a UK year the gap between panels is smaller, because many hours are cool. More on this in solar panels in hot weather.
Efficiency: it matters when roof space is tight
Efficiency tells you how much power you get from each square metre. The four panels in the table range from 22.02% to 24.3%, and they are all close in size: just under 2 m² per panel (1,762 × 1,134 mm is 1.998 m²).
In practice: suppose your roof has room for 10 panels. With the 440 W panel that is 4.4 kWp; with the 485 W panel it is 4.85 kWp, about 10% more capacity from roughly the same 20 m². On a roof where space limits the number of panels, that difference can justify paying more per panel. On a roof with room to spare, a less efficient but cheaper panel reaches about the same kWp with one more panel (11 × 440 W = 4.84 kWp), which can cost less overall; compare the whole-system price to see which is cheaper. How to work out how many panels fit is in solar panel sizes.
Glass-glass or single glass: weight and build
The second visible difference is the construction. The Trina panel is dual glass (1.6 mm front and 1.6 mm back); the other three are single-glass, with a 3.2 mm front glass.
- Dual glass puts a second pane of glass on the back of the panel. To judge durability, compare the load ratings and warranty terms of the specific model: the Trina datasheet in the table carries a 30-year power warranty.
- Weight varies little between the four (20.6 to 22 kg), but on an older roof the total counts: ten panels weigh between 206 and 220 kg, before the mounting rails.
Your installer is the one who checks the roof. Ask for the chosen panel's weight and the mounting system to be written into the quote.
Bifacial panels: when they make sense
A bifacial panel also collects light on its back face, from light reflected by the surface behind it. The gain depends on the panel, on what is underneath and on how far away it is: a pale, reflective surface and an air gap behind the panels help; panels fixed close to a pitched tiled or slate roof get very little.
If a quote offers bifacial panels on your roof, ask how much rear-side output has been assumed, and with what assumptions about the gap to the roof and the reflectivity of the surface. A figure measured on a ground-mounted array does not carry over to a house roof.
Bifacial panels are worth discussing for carports, pergolas, garden canopies and ground-mounted arrays, where the back of the panel actually sees light.
How to choose, in three scenarios
- A large, unobstructed roof. Efficiency is not the deciding factor: choose on the price of the whole system per kWp and on the warranties, and check the temperature coefficient.
- A small or awkward roof (dormers, hips, vents or only a few usable rows). Here efficiency decides how many kWp fit: the more efficient panel can be worth the extra cost, so compare kWp achievable on your roof, not the price per panel.
- A lighter structure or a roof that needs checking. Look at weight and glass type, and ask for the roof to be checked before the panel is chosen.
In all three cases, the final comparison is the price of the complete installed system per kWp. Solar panels supplied and fitted by an installer in your home currently have 0% VAT. This is scheduled to rise to 5% on 1 April 2027 unless extended. Kits bought without installation carry 20% VAT. How to read a quote line by line is in comparing solar quotes, and what the warranties cover over time is in how long do solar panels last.
Frequently asked questions
Which is better, monocrystalline or polycrystalline?
Monocrystalline produces more power per square metre, and none of the four manufacturer datasheets we compared uses polycrystalline cells. Beyond that, compare specific models: power for your roof space, the complete price, behaviour in heat and the warranties. The cell type alone is not enough to choose.
What do "N-type", TOPCon, ABC and HPBC mean?
N-type describes the kind of silicon; TOPCon, ABC and HPBC describe how the cell is built. They are not quality grades: judge them by what they do to the panel's figures, above all efficiency, temperature coefficient and warranties.
How efficient are solar panels today?
On the four panels in our table, maximum rated efficiency ranges from 22.02% to 24.3%. That is a product figure: it applies to those models in those datasheet editions, so read it again on the datasheet of the panel you are offered.
Are bifacial panels worth it on a pitched roof?
Usually not much. The gain depends on reflected light reaching the back of the panel, and with panels fixed close to the roof very little gets there. They make more sense on carports, pergolas and ground-mounted arrays. Ask for an estimate of the rear-side contribution for the layout proposed.
How much roof space do 10 panels need?
Each of the four panels in our table is just under 2 m², so 10 panels cover about 20 m² of panel area, plus the spacing and edge clearances the mounting system needs. With these panels, 10 panels give between 4.4 kWp (440 W panels) and 4.85 kWp (485 W panels).
Does the panel type affect the Smart Export Guarantee or loans?
No. The cell type does not change eligibility. For the Smart Export Guarantee (Great Britain only), a home system needs an MCS-certified (or equivalent) installation and installer. The UK-wide Warm Homes Loan Scheme, launching from September 2026 through approved lenders (none had been named on 23 September 2026), will require an MCS-certified product and an MCS-certified installer. Lenders set their own rates and checks.