Short answer
Monocrystalline panels are made from a single piece of silicon crystal and give more power than polycrystalline in the same area; most panels on the market today are this type. Polycrystalline panels are made of multi-crystal silicon, are less efficient and are becoming rarer. Bifacial (double-sided) panels also collect light reflected onto the rear surface; they give extra production over a light-colored ground and with a mounting raised off the ground.
Where does the difference between panel types come from?
The cells that make up a solar panel are made of silicon. If the silicon has a single, regular crystal structure it is called monocrystalline; if it is formed by many small crystals joined together it is called polycrystalline. In a single-crystal structure electrons move more easily, which lets you get more electricity from the same surface.
You can also tell them apart by eye. Monocrystalline cells are dark, almost black, and an even color. Polycrystalline cells are bluish and slightly shiny, with patterns that look like broken glass inside. Bifacial panels look like monocrystalline from the front, but their rear surface is glass or transparent instead of an opaque foil.
Monocrystalline panel: today's default choice
Monocrystalline panels give higher power per unit area. For homes and businesses with limited roof area, this is a direct advantage: a more powerful system fits on the same roof. With advances in production technology, monocrystalline panels have come to make up most of the market, so most of the panels you get quotes for will be monocrystalline.
In quotes, next to the word monocrystalline you may see terms like PERC, TOPCon and half-cut. These are details about the cell's production technique and the panel's internal wiring. In half-cut panels the cells are divided in two; this structure helps reduce losses in partial shade. You find out which technology makes sense for you by comparing the values in the panel's datasheet.
Polycrystalline panel: is it still chosen?
Polycrystalline panels were common at one time because of their lower cost. Today their production has decreased and they are less available on the market. In systems where space is not a problem, for example on a large piece of land, the efficiency difference matters less. But if a polycrystalline panel is offered in a new project, it is worth asking whether this is a deliberate choice or a way to clear existing stock.
If you will add to an existing polycrystalline system, connecting panels of a different type and power to the same string can cause problems. In that case the new panels are connected to a separate string or a separate inverter. This way the low current of the old panels does not pull down the output of the new panels, and the two groups can be monitored independently of each other.
If you are thinking of replacing your existing polycrystalline panels with new ones, first look at their actual production. If the values in the monitoring app meet expectations and there are no cracks, discoloration or hot spots on the panels, removing working panels is often an unnecessary expense. If there is room left on the roof, adding the new monocrystalline panels as a separate string can be a more sensible way.
Bifacial panel: light from behind
Bifacial panels collect light from the rear surface as well as the front surface. The light reaching the rear is light reflected from the ground and surrounding surfaces. So to get extra production from a bifacial panel there are two conditions: a light-colored ground under the panel that reflects light, and the panel standing high enough above the ground.
In ground-mounted installations, a bifacial panel can make sense on light-colored soil or gravel with a raised structure. It can also be considered on flat roofs covered with a white membrane. On the other hand, on a sloped tile roof, the rear of a bifacial panel mounted flush against the roof sees almost no light; in that case the extra cost does not pay off.
Because both the front and rear of bifacial panels are glass, their weight and mounting details can differ. The structure is chosen accordingly, and beams that would shade the rear surface are avoided.
Expert note: If a bifacial panel is offered, ask what ground and mounting height assumptions the extra production estimate was based on. If the assumption does not fit the site, the extra production will not happen either.
What changes with heat and dust?
All panels lose power as they heat up. How much is lost is written in the panel's datasheet as the temperature coefficient. In a region with hot summers like Şanlıurfa, this value is one of the main criteria to look at when deciding between two panels. A panel whose coefficient has a smaller absolute value loses less power in the heat.
On dust, there is no clear difference between panel types. Every panel's production drops with dust, and regular cleaning is needed. The panel's frame structure and edge details affect how rainwater carries the dust; panels whose frame traps dust can form a band of dirt along the lower edge.
What to look at in the datasheet when choosing a panel?
When deciding, the panel's technical values and the manufacturer's reliability say more than its type. When you get a quote, ask for the following information in writing:
- Panel power and efficiency value
- Temperature coefficient
- Panel dimensions and weight
- The manufacturer's product and performance commitment terms
- International test and certification documents
- Authorized dealer and service information in Türkiye
Which one when?
For home and business roofs, a monocrystalline panel is in most cases the most sensible choice; the space is used efficiently and the product is easy to find. On large land with a raised structure and a light-colored ground, a bifacial panel can be considered. A polycrystalline panel comes up in special cases such as compatibility with an existing system.
The final decision is always made according to the site. When roof size, mounting method, shade and budget are considered together, you may see that the highest-efficiency panel is not always the right choice.
Let's think through an example: on a small, unshaded house roof, a high-efficiency monocrystalline panel provides the most energy that can be had from the limited area. On the other hand, in a raised ground system built for a pump on light-colored soil in the Harran Plain, the rear of a bifacial panel works too. The same panel produces different value at two different sites.
When discussing panel type, also remember inverter compatibility. The panel's voltage and current values determine how many panels can be connected in series to the inverter. When the panel changes, the string design changes too; that is why the panel and the inverter are chosen together.
Frequently asked
Which is better, monocrystalline or polycrystalline panels?
In the same area, a monocrystalline panel gives more power and is more common on the market today. A polycrystalline panel still works where space is not a problem, but it is chosen less often in new projects.
Can a bifacial panel be mounted on a roof?
It can, but for extra production, reflected light must reach the rear of the panel. On a bifacial panel installed flush against the roof, there is very little of this light. It makes more sense on flat roofs with a white membrane and with raised mounting.
Are panels that look black more efficient?
Color alone does not show efficiency. Monocrystalline cells are dark, but to understand efficiency you need to look at the power, efficiency and temperature coefficient values in the panel's datasheet.
Let's choose the right panel for your roof together
Share your roof or land details; Desa Bilişim will put the different panel options side by side with their datasheets and prepare a written quote.
