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Efficiency of solar panels

The performance of solar panels is something to take into account if you are thinking of a self-consumption installation. The more performance a solar panel has, the more energy you will generate in the same space (the roof of your home, for example).

We explain it below, as well as a classification by sizes and powers related to the performance of solar panels.

What is the efficiency of a solar panel?

The efficiency of a solar panel is the amount of energy that a photovoltaic solar panel is capable of generating based on the incident solar energy it receives .

It is typically considered, in optimal conditions, that the sun “sends” an irradiance of 1000W/m2 of power. And from that data, we will be able to know the efficiency that a solar panel has.

What is the performance of a solar panel?

Although they are often confused, efficiency is not the same as performance. We understand the performance of a solar panel, the empirical behavior that it will have in real working conditions.

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In other words, how good is that panel going to be when it’s really put to work.

How to know the performance of a solar panel?

Theoretical calculation under standard measurement conditions

The way to calculate the efficiency of photovoltaic panels, that is, the amount of energy they receive from the sun and that they can transform into electricity , is simple. First of all, you should keep the data that we mentioned before. Namely:

In optimal conditions, or STC (Standard Measurement Conditions), with a panel temperature of 25ºC and an AM spectral distribution of 1.5G, it is considered that a solar panel receives an irradiance of 1000W/m2.

How many watts does a solar panel generate then?

Imagine that you have a panel with dimensions of 2m x 1m. This means that the surface of the panel is 2m2.

If that panel were perfect, without losses, with 100% efficiency, then it could generate 2m2 x 1,000W/m2 = 2,000W of power. Obviously this is utopian and real solar panels do not have that efficiency.

How much does a solar panel produce per m2?:

Let’s say you have a 400W solar panel that is 2 meters long and 1 meter wide. That is, in optimal conditions, it means that this panel can generate 400W.

If we have said that, in optimal conditions, the sun provides 1,000W/m2, we would have the following:

Panel area: 2m2

Panel power: 400W

Irradiance: 1000W/m2

Panel Efficiency:

Remember, do not confuse Performance with Efficiency. The performance is the empirical behavior that the solar panel will have in working conditions, but the efficiency is something else:

(Panel Output Power) / (STC Irradiance) * (Panel Surface in m2) = 400W / (1000W/m2 x 2m2) = 0.20 -> 20% Efficiency

Or in other words, that solar panel takes advantage of 20% of the solar energy that falls on it. And that’s if we don’t talk about how it affects the inclination of the solar panels .

And although it is not directly related, as an aside, we always talk about new panels. Second-hand solar panels are always NOT recommended, because they will never have the performance of the first day, nor the guarantee nor any advantage over new ones.

Efficiency is also usually given per square meter:

It can also be interpreted based on the performance of a solar panel per square meter. In other words, in this case, this solar panel would have a performance of 200W per square meter.

Now we will delve deeper into which are the highest solar panel efficiencies, the most common and classify them by size and power.

How to know the performance of a solar panel?

You should analyze these simple guidelines to know if a panel will perform well or poorly:

  • Do you use solders between your cells? : If the answer is YES, there are many possibilities of failure of the panel. Always avoid panels that use welding .
  • What coefficient of degradation does it have? : If it is greater than 0.7-0.8%, discard it. The lower the degradation coefficient, the more energy the panel will produce throughout its life. There are panel models with only 0.25% annual degradation, such as SunPower’s MAXEON, as a maximum performance reference.
  • What temperature coefficient does it have? : The lower the better it will perform when the sun shines and the panel heats up. Temperature greatly affects the performance of a panel .

Analyze these 3 data of a solar panel well and you will be sure that it will have a good performance.

Efficiency Classification of Photovoltaic Panels

By dimensions, powers and high efficiency

In today’s market you can find a wide variety of solar panels, yields and efficiencies. It is true that the lower the performance of a solar panel, the lower its price, and vice versa.

The most common is to find solar panels with these efficiency ranges:

  • Solar panels with efficiencies between 16-17%. What we call, medium-low efficiency.
  • Solar panels with efficiencies between 18-19%. It would already be a medium-high efficiency.
  • Solar panels with efficiencies above 19%. There we already talked about the most efficient solar panels .

In this regard, we are going to make a small classification by efficiencies, sizes and standard powers that you can find in the current photovoltaic market.

Efficiency by Powers and Measurements of Solar Panels:

As you well know, solar panels are composed of silicon solar cells (mono or poly) and generally the configuration of the panels is usually 60-cell and 72-cell solar panels.

Solar panels with 60 cells usually have dimensions around 1.7m x 1.0m approx, and those with 72 cells, 2.0m x 1.0m approx. Although you can make slight variations.

These are the most common measurements of solar panels with their power and efficiency:

panel power  Solar panel measurements Efficiency %
250W Solar Panel 1.7m x 1.0m 14.7%
260W Solar Panel 1.7m x 1.0m 15.2%
270W Solar Panel 1.7m x 1.0m 15.8%
280W Solar Panel 1.7m x 1.0m 16.4%
300W Solar Panel 1.7m x 1.0m 17.6%
310W Solar Panel 1.7m x 1.0m 18.2%
320W Solar Panel 1.7m x 1.0m 18.8%
330W Solar Panel 1.7m x 1.0m 19.4%
330W Solar Panel 2.0m x 1.0m 16.5%
340W Solar Panel 2.0m x 1.0m 17%
350W Solar Panel 2.0m x 1.0m 17.5%
370W Solar Panel 2.0m x 1.0m 18.5%
380W Solar Panel 2.0m x 1.0m 19%
390W Solar Panel 2.0m x 1.0m 19.5%
400W Solar Panel 2.0m x 1.0m twenty%
410W Solar Panel 2.0m x 1.0m 20.5%

It goes without saying that any installation, whatever the size of the panel, must be installed on a solar panel support on the roof, never directly.

High Efficiency of Solar Panels:

Going one step further in solar panels and efficiencies, we now show the table of the most efficient solar panels that exist:

Maker Model Efficiency Power Size
SunPower SPR-X22-370 (Now MAX3-400) 22.6% 400W 1,690 x 1,046mm
SunPower SPR-X22-360 (Now MAX3-390) 22.1% 390W 1,690 x 1,046mm
SunPower MAX3-370 20.9% 370W 1,690 x 1,046mm
LG Neon LG360Q1C-A5 20.8% 360W 1,700 x 1,016mm
LG LG355Q1C-A5 20.6% 355W 1,700 x 1,016mm
AUO SunForte PM096B00 20.6% 335W 1,559 x 1,046mm
SunPower MAX2-360 20.4% 360W 1,690 x 1,046mm
AUO SunForte PM096B00 20.3% 330W 1,559 x 1,046mm
SunPower MAX3-350 19.8% 327W 1,690 x 1,046mm
SHARP NQ-R256A 19.8% 256W 1,318 x 980mm
panasonic VBHN330SJ53 19.7% 330W 1,590 x 1,053mm
panasonic VBHN325SJ53 19.4% 325W 1,590 x 1,053mm
SunPower SPR-P19-400 19.4% 400W 2,067 x 998mm

You can get more information about these high-efficiency models in our blog article: The Highest Efficiency Solar Panels .

PERC cells in High Performance Solar Panels

What are the best performing solar panels?

This is a question that is almost repeated like a mantra, and the truth is that the answer has always been the same:

The panels that present the best performance are those that are made up of monocrystalline cells.

It does not matter whether it is in hot or cold climates, Mono always performs better than Poly, you can check it in Types of Monocrystalline or Polycrystalline Solar Panels

This is, among other things, because the efficiency of monocrystalline photovoltaic cells is greater than the efficiency of polycrystalline cells.

What happens is that, due to the demand for market prices, most of the solar panels installed in the world are polycrystalline.

Although the trend is changing, we must bear in mind that the manufacturing process for monocrystalline cells is more expensive than that for polycrystalline cells, so this has a direct impact on the prices of solar panels that later reach the market.

What happens is that now manufacturers of solar panels, such as the American brand of solar panels SunPower , have gone a step further and have begun to manufacture using a new technology called PERC (Passivated Emitter and Rear Contact).

Do you remember the phrase… the polycrystalline panel has better heat performance than the monocrystalline?. Well, that no longer happens with the Mono PERC, the performance is much higher than any polycrystalline panel in any situation.

So if you are looking at solar panel prices, it will be good for you to read this article first.

What does this new PERC photovoltaic cell technology consist of?

Basically, and without going into too much detail, Mono PERC solar cells incorporate a sheet on the rear face of the cell that, on the one hand, allows  greater capture of sunlight , and on the other,  greater capture of electrons .

With this, what is achieved is a greater uptake of electrons, which is why more electricity is generated and, consequently, greater power.

We see an image of what the back of one of those PERC photovoltaic cells looks like:

Let us now see some illustrations that will help us understand what we have said about the  greater light capture  and  greater electron capture  in PERC cells:

Efficiency of solar panels

This first image shows the difference in sunlight harvesting between a standard solar cell and a PERC solar cell. What is shown is how, in the standard cell, a large part of the sunlight leaves and/or is absorbed by the back of the cell, so it is wasted.

However, in the PERC cell, part of this radiation, which was wasted in the standard cell, is recovered and used thanks to a  special insulating layer  (white line in the figure) located between the silicon and the subsequent aluminum layer.

In addition to this, this insulating layer has holes made by laser that optimize the subsequent capture of electrons. Interesting, right?

Now let’s look at another illustration to see the enhancement of electron uptake.

Although the image shows it clearly, what can be seen is how, in the standard cell, a large part of the electrons end up on the metal back side of the cell, however, in the PERC cell, the insulating layer that we mentioned earlier allows that a large part of these electrons are recovered and captured by the emitting layer (the visible face of the cell, let’s say it that way), so that  greater current is achieved  and, consequently,  greater power .

What other advantages does the use of solar panels with PERC cells have compared to the standard ones?

Well, if those were not enough reasons, here are some more, just as interesting as the ones mentioned:

  • PERC technology  performs better in low light environments  than standard poly and mono panels.
  • PERC cells outperform those used in traditional panels in  early morning  and  late afternoon , as well as in  cloudy environments .
  • They generate less heat  than traditional cells, thus improving performance in high temperature latitudes.

As always, an image is worth a thousand words, so we are going to provide 2 more images, in this case 2 graphs generated by PVsyst where we are going to see the difference between photovoltaic panels with PERC technology and traditional ones:

  • Comparative performance graph:  In this first graph we can see a comparison of the relative efficiency of one panel with respect to the rest. In other words, it shows how much better the performance of a traditional Poly photovoltaic panel, traditional Mono… is with a Mono PERC solar panel.
    As you can see, and as we have already mentioned,  the PERC models are the ones that  have the best performance:

  • Comparative technology graph:  In this second graph, what we can see is the same as in the previous one, but in a more summarized way, that is,  comparing traditional technology with the new PERC photovoltaic panel technology :

Efficiency of solar panels

Of course, in addition to the above, they incorporate diodes and junction boxes for solar panels , like any other on the market today.

The VERY high performance technologies:

But if you are really looking for truly high performance and, above all, long-lasting, so that your photovoltaic system produces almost twice as much, during the average life of a good panel for 40 years, then you should go for Type N IBC and HJT technologies.

Both are by far the two most performing and durable technologies out there. In other words, more performance, more durability, implies much more energy generated throughout the useful life of an installation.

We hope you found it useful and, as always, anything you need, we remain at your disposal.

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