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How efficient are solar panels?

A look at the various factors impacting solar panel efficiency.

6 min read

With increasing awareness about climate change and soaring energy bill costs, renewable energies have been pushed to the forefront as a viable solution to energy problems.

In recent years, solar panels have become much cheaper to produce, making technologies that boost solar panel efficiency even more affordable. The question remains, though: how efficient are solar panels?

This article will go through the different factors that reduce or boost solar panel efficiency, and will also present some of the most efficient brands on the market.

Which factors determine the efficiency of solar panels?

Many factors come into play when determining the efficiency of a solar panel. The first is the structure of the panel.

Each solar panel is made up of cells, the building blocks of solar panels that convert solar energy into DC current. The efficiency of these cells, then, is a major determining factor in the efficiency of the whole panel.

Cell efficiency is defined by the structure of the cell, notably by the type of silicon used during production. Silicon is purified and then cut into thin wafers. These wafers serve as the base of the panel.

Once the silicon is purified, it can be treated with different chemical elements. To create a positive charge (P-type), phosphorus is added to the silicon; for a negative charge (N-type), boron is added to the panel.

Most solar cells are given a positive charge, due to its lower production costs. In recent years, however, declining N-type silicon wafer manufacturing costs have led to an increase in their production.

N-type silicon is attractive as it can produce more energy than its positively-charged counterpart. Also, N-type silicon is less prone to LID (light induced degradation), a decline in solar panel efficiency when first exposed to sunlight -- an estimated loss of 2% to 3% of its original wattage.

With reduced production costs, N-type silicon wafers are becoming an increasingly affordable and efficient option.

As well as the cell type, overall efficiency is also affected by the connection between the cells and the colour-the darker the panel, the more heat absorbed, resulting in a decrease in cell efficiency.

Environmental factors also come into play, with outside temperature, the irradiance level (measure of solar power), and panel’s angle and inclination on the roof all influencing overall efficiency.

What types of solar panels are the most efficient?

Solar panels efficiency
Solar panels can be made from different types of materials, which affect overall efficiency. Efficiency of a material is calculated under test conditions, the ideal conditions for generating solar energy.

As an example, a solar panel of 1m2 with an efficiency of 19% would produce 190 Watts.

With this in mind, let’s take a look at the efficiency of these materials


Monocrystalline panels are made from the purest available silicon and can be called single-crystalline cells. Monocrystalline panels have the highest efficiency, at an average of 22-27%.


These panels are made from multiple crystals, so are not pure silicon. They are less efficient than monocrystalline panels, with an efficiency of 15-22%.

Passivated Emitter and Rear Cell (PERC) panels

PERC panels are an exciting new type of solar panel. They have been designed to maximise energy production by increasing the number of electrons that are captured by the panel.

With the addition of a passivation layer, more electrons are extracted from solar cells, thus producing more energy and increasing efficiency.

Although exact efficiency of PERC panels has not been determined, test conditions have shown that these panels show a 12% higher efficiency than monocrystalline and polycrystalline panels.

PERC technology is also rapidly improving, meaning that efficiency will only improve in the coming years.

Thin-film solar panels

The cheapest type of solar panel, the thin-film panel, is also the least efficient. Efficiency comes in at 15-22%.

The efficiency of solar panels under extreme weather conditions

Solar panel on a house
When producing a solar panel, manufacturers must ensure the longevity of their product. Unsurprisingly, however, extreme weather affects solar panel efficiency and may deteriorate the product.

  • Snow: after 5cm of snow has accumulated on the panel, all efficiency is lost, meaning that the panel no longer produces energy.
  • Wind: one of the major factors that leads to solar panel damage, leading to reduction of efficiency.
  • Hail: solar panels have been designed to resist damage from hail.
  • Ice: if there is no solar coating, ice can represent a major loss of efficiency (25-100%), meaning that thin-film panels are at risk.
  • Rain: can lead to a chemical residue on the panel, which is responsible for a slight loss of efficiency (0.2%).

You can read more about solar panels in extreme weather conditions in this article.

Four key things to look for when choosing solar panels


The price of solar panels remains a major determining factor in choosing a panel. As a general rule, the more efficient the panel, the more it will cost.

The same solar panel system, for example, will cost around £1-1.5 per watt for monocrystalline and £0.9-1 per watt for polycrystalline.


Efficiency is key when you buy a solar panel as it determines how much energy you produce. So the more efficient a solar panel, the more energy you have for your home.

Having a more efficient panel will make you more independent in terms of energy production and help alleviate the financial strain of rising bill costs.


Silicon-based panels (monocrystalline and polycrystalline) have a longer lifespan than thin-film panels -- 25 years compared to 20 years.

The lifespan is key, as a longer durability will mean your maintenance costs in the future will decrease. It also reduces the overall carbon footprint of the solar panel's installation.


Aesthetics also play a role in what solar panel you might buy.

The standard solar panel is blue with a visible grid. Many people dislike this aesthetic. If you are one of these people, a sleeker black panel without a visible grid might be for you. Keep in mind that a more modern style might affect efficiency.

Top 10 most efficient solar panels

If you are interested in buying a solar panel, here are some of the most efficient panels:

Why efficiency matters

Efficiency determines how much energy you produce. More production from your solar panel means that you are more energy independent.

With energy independence, rising bill costs will become less daunting, as you are much less reliant on national energy production.

If you have a solar panel battery, under the SEG scheme, you can sell surplus energy back to the grid. So with a more efficient panel, you will have more surplus energy and thus more money will be made from the solar panel.

To sum it up

Solar panel efficiency has only been on the rise with cutting-edge technologies becoming more affordable and more mainstream.

The dilemma remains, however, for the consumer to select a solar panel that prioritises efficiency or affordability. Whereas some solar panels are more expensive, they perform better in terms of energy production and will incur much lower maintenance costs.

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Which solar panels are most efficient?

Silicon-based panels are most efficient, notably PERC panels.

Are thin-film panels efficient?

Though they remain an affordable option, thin-film panel efficiency is noticeably lower.

Are there efficient solar panel brands on the market?

Yes, SunPower solar panels are the most efficient option available on the market at the moment.

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