Give me that sun: Efficiency and world’s most efficient solar panels in 2023

Efficiency is a big, loud, almost frightening word. People all around want everything to be as productive and as fast as possible. What does being efficient mean for solar panels and how important is it if you want to switch to solar? We'll guide you through these questions and provide a thorough efficiency comparison of solar panels with the highest indicators on paper. Hopefully, in the most time-efficient way possible.

Top-5 most efficient solar panels: comparison table

Here are the most efficient panels from top electronics brands as of summer 2022. The best models from other popular solar manufacturers float between 21% and 21.5%. We decided not to include bifacial solar panels in this rating. If we did, they would take all the top places: up to 30% production bonus gives them efficiency that can get over 25%.

Efficiency doesn’t always mean high costs. While solar panels by Sunpower, LG, Panasonic and REC are rather costly, Canadian Solar offers relatively inexpensive PV modules. They come at $0.6–$0.9 per Watt.

Solar panel efficiency shows how much sunlight it turns to DC

The efficiency of a solar panel or its energy conversion rate indicates how much sunlight this particular module can turn to usable direct current. A 19% efficient panel turns 19% of the sunlight that it gets into electricity under Standard Test Conditions. Today the efficiency of solar panels generally varies from 17% to 22%. The most efficient models are just shy of 23%.

You might wonder: why don’t solar panels turn all of the sunlight into electricity? The modules actually can’t make use of certain wavelengths of solar radiation. Besides, the conversion process itself is not perfect and lots of energy gets lost. The solar industry has come a long way though: first silicon panels that appeared in 1954 had only a 6% conversion rate!

Efficiency depends on how modern the solar panel is

The distance between 6% conversion rate and 20% is a long one. How did the engineers bridge that gap, and what makes the panel more or less efficient to begin with?

Read also

Types of solar panels: The efficient, the cheap and the flexible

The type of panel that you use plays a major part. Today monocrystalline panels are the most efficient and the majority of solar brands don’t even make anything else. Manufacturers like Canadian Solar still toy around with polycrystalline panels, but their conversion rates aren't nearly high enough: around 14–17%. Thin-film panels were by default the least efficient type of panels out of three, but they are still being developed, modernized and have a bright future.

Several technologies serve to maximize the energy conversion rate of a module as well.

PERCs or Passivated Emitter Rear Cells

Each cell is manufactured in such a way that it can reflect the sunlight in itself and use it again. PERCs modules’ efficiency is 1% higher than that of standard solar panels.

Half-cut cell design

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Strength in numbers: How half-cut solar cells conquer the market

Engineers split solar cells with a laser, making them two times smaller. The resistance inside a cell decreases, the electrical losses fall and you get more current. Half-cut design was introduced by REC in 2014 in its TwinPeak panel. Half-cut cell panels are 3–4% more productive than modules with standard cells.

Heterojunction technology

Engineers enclose a solar cell in ultra-thin layers of silicon. Not only does it slightly increase efficiency, it allows the panel to retain high production levels at high temperatures. In particular, Panasonic and REC use this technology, which makes their panels exceptional in hot areas.

Multi busbars technology

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Trina Solar panels review 2023: Benefits of science

Busbars are thin ribbons of copper that connect solar cells and conduct the current between them. The problem with traditional busbars is that these ribbons shade the cell slightly. That’s why engineers started using thin wires instead and improved the efficiency by increasing the active surface of a panel. Trina Solar is the pioneer of multi busbars technology.

IBC cells

Interdigitated back contact cells have contacts on their backside and they don’t get in the way of solar production at all. That’s the signature technology of SunPower, although other brands try it out as well. Unfortunately, this design increases the manufacturing costs which reflects in Sunpower prices.

N-type cells

P-solar cells are the most widespread type, but N-type cells have become more and more popular in recent years. They are more efficient and lose less power in the first year of operation. Trina Solar experiments with n-type cells a lot: for instance, it tries to lower manufacturing costs by increasing the size of a wafer.

Most brands are fine with using only a few of these innovations in their modules. Implementing all of them at once drives the manufacturing expenses way up. So while LG and Sunpower did win in our solar panel efficiency comparison table, the cost of this victory is high.

External factors affect the efficiency as well

Even if your panel is packed with the latest innovations, its production levels may be brought down by real-world factors:

Location and sun hours

Some areas just have more sunlight throughout the day than others, therefore the irradiance of panels in these sunny places is higher on average. Even if your panels aren’t all that efficient, they will harvest more solar energy in Los Angeles than our Top-5 modules would do somewhere in Alaska.

Weather conditions and shading

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Shedding light on solar panels shading

Bad weather brings the performance of solar panels down by 10–40%, depending on the model and thickness of the clouds. Shading is much more problematic, since cells in most panels are connected in series. If one cell doesn’t get any sunlight, it brings the production of the whole row. Solar panels by Canadian Solar and Q CELLS remain efficient even in low-light conditions.

Positioning and angle

Solar panels in the northern hemisphere and in the USA in particular should be facing south. It’s not always the option, but picking west or east makes panels 15% less productive. The angle of panels should be equal to your latitude or just set between 30 and 45 degrees — its impact on overall efficiency is relatively minor.

Temperature

The best weather for solar panels is cold and sunny. When it gets too hot, the panels start to lose efficiency. This is what the temperature coefficient shows — how much output the panel loses for each degree after 25 °C at which it is tested. Usually, the coefficient varies between −0.3%/°C and −0.5/°C.

In stock

Aptos Solar 365W Solar Panel 120 cell DNA-120-MF26-365W

• Rated Power Output 365 W
• Voltage (VOC)40.7V
• Cell number120 cell
• Cell TypeMonocrystalline

Pickup on Tue, Oct 03 from Cranbury, NJ

Delivery on Oct 06–11

$304^.78

Add to cart

Let’s set an example. The Aptos Solar 365 W panel has a temperature coefficient of −0.36%/°C. The solar panel’s temperature is always higher than the air ambient temperature. On a sunny day Aptos module heats up to 44 °C, which is marked as Nominal Operating Cell Temperature (NOCT) in the datasheet. Let’s see how much output it provides in these circumstances:

REC and Panasonic engineers use heterojunction cell technology that gives their panels lower temperature coefficients — around −0.25%/°C.

Time of year

This one is pretty straightforward — there is just less sunlight in the winter and fall compared to spring and summer. The irradiance falls and so does the efficiency. In June-July panels generate about 50% more energy than in December-January.

Calculating the efficiency of a Q CELLS panel

Let’s round up our explanation of efficiency concept by learning how to calculate the conversion rate of a solar panel.

Power output can be easily found in the solar panel spec sheet. Area of panel means the whole area of a panel, not just its active surface. In the past there were brands that increased the efficiency numbers of their panels on paper by not including the frame in calculations (not fair!). Standard solar irradiance in lab conditions is 1000 W/m² which is roughly equivalent to a sunny day.

Out of stock

Q CELLS 350W Solar Panel 120 cells Q.PEAK DUO G6+

• Rated Power Output 350 W
• Voltage (VOC)40.73V
• Cell number120 cell
• Cell TypeMonocrystalline

Delivery on Oct 06–11

Let’s do the math ourselves. Imagine we have a Q CELLS Q.PEAK DUO G6+ panel which gives 350W output and is 68.5​ x 40.5​ inches in size (or 1740 × 1030 mm). Therefore the area of a panel is 1.7922 m². Let’s calculate the efficiency:

Did we do it right? According to the datasheet, the efficiency of a 350W module is indeed equal or greater than 19.5%.

Efficiency is a good but not the most important metric

Ok, but what does having a highly efficient panel mean in practice? Let’s say, we have two panels of the identical size. One of them is polycrystalline and has 14% efficiency. The other one is monocrystalline and has a 21% conversion rate or 50% more than the first one. Since panels are the same size, the power output of a monocrystalline panel should be 50% greater and it should provide you 50% more energy in kWh. Here the comparison of solar panels efficiency shows massive difference which is multiplied by the number of panels that you have.

But what if we have two panels of the same power output but with slightly different efficiencies? Well, they are going to provide just the same amount of energy, but the more efficient panel is going to be slightly smaller.

If space is not a constraint for you, then efficiency is not the most important metric to look out for. Keep in mind, however, that a typical residential system consists of 15–35 panels: the bigger the system, the more significant the panel size becomes. Having efficient panels is especially important in a mobile installation. On a boat or on an RV, you might have room for only a couple of modules.

Here’s the bottom line: while it’s easy to compare solar panels efficiency, by itself it becomes a deciding factor only in specific situations, such as high energy needs combined with lack of space. Otherwise, we suggest paying more attention to power output of a panel, price and warranties.

Illustrations – Natalya Absalyamova

Andrey Gorichenski

Senior Editor

Andrey had been a news editor and freelance writer for a number of medias before joining A1SolarStore team. Climate change and its impact on people's lives has always been among his interests and it partially explains his degree in Philosophy and Ethics.

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