Solar Panel Efficiency

Solar panel efficiency ratings are currently between 15% to a maximum of 22%. The higher the efficiency rating, the more energy your panels are going to be able to produce.

Here are some of the factors that affect solar panel efficiency.

The location of your solar panels
The tilt angle of your solar panels
The weather conditions in your area
How well you maintain your solar panels
The build quality of your solar panels
The number of peak daylight hours in your area

Today, we are going to provide you with a full rundown of what solar panel efficiency is alongside the many factors that affect it.

1. What Is Solar Panel Efficiency?
2. How Efficient Are Solar Panels?
3. What Is the Most Efficient Solar Panel?
4. Factors That Affect Solar Panel Efficiency
5. How Can We Increase the Efficiency of Solar Panels?
6. Solar Panel Efficiency FAQ
7. Conclusion

What Is Solar Panel Efficiency?

Solar panel efficiency is measured as a percentage (ranging between 15% to 22%) that determines how much energy a solar panel is able to produce over the course of a year. This is also referred to as solar panel performance.

Certain factors affect solar panel efficiency.

Higher for monocrystalline solar panels
Lower for polycrystalline and thin film solar panels
Measured in watts per meter

Based on a number of different solar panel types carrying varying efficiency ratings, here is how much energy you can expect to produce when using solar technology.

Solar panel efficiency	15%	18%	22%
Solar panel output per square meter	150 watts	180 watts	220 watts

The above figures are based on ideal conditions for the panels in terms of placement and peak daylight hour access. Currently, the upper figure of 220 watts per square meter is realistically the most power that you will ever be able to harness from a solar panel.

Can Solar Panels Be 100% Efficient?

It is currently impossible for solar panels to be 100% efficient. The maximum efficiency rating available for any commercial solar panel sits at roughly 22%. Some premium models may be able to achieve more. Figures of as high as 26% may be possible.

However, solar technology is rapidly advancing. There have been several experiments conducted with a material known as gallium arsenide (abbreviated as GaAs) that have proven fruitful.

Is Solar Panel Efficiency Improving?

In the year 2020, a renewable energy research team from the National Renewable Energy Laboratory in Colorado was able to produce a solar panel using GaAs that reached a staggering 47.1% efficiency rating.

As such, it is very likely that over the next few years, solar panels will be capable of achieving efficiency ratings of 50% and possibly even more.

Since this technology is cutting edge, the costs will initially be very high when this technology is released on the market. Eventually, these panels are likely to become accessible to the masses in the same way that electric cars are now.

It is entirely feasible based on these developments that one day, solar panels will be capable of achieving 100% efficiency.

How Efficient Are Solar Panels?

Now that you understand what solar panel efficiency is, you are going to want to know the answer to the golden question. How efficient are solar panels? Or to present the question in a slightly different way, are solar panels efficient enough to cover all your energy needs?

You will be pleased to know that they are. Here is the information that you really need to know.

The average American home uses 10,649 kilowatt hours per year.
By using anywhere from 17–42 solar panels (depending on their power output capacity), you can cover 100% of these energy requirements.

Through going solar, you really can cover 100% of the costs of your energy bills thanks to the high efficiency rating of solar panels. Even if you do not have a big enough system to cover 100% of your requirements, you can still shave off an enormous chunk of your bills through going solar.

This all relies on you having the most efficient solar panels possible that have been placed in the most optimal position for them to be able to maximize their power output.

What Is the Most Efficient Solar Panel?

Forgetting about the previously mentioned GaAs solar panels that are currently in testing and at the concept stage, monocrystalline silicon solar panels are currently the most efficient solar panels available with an efficiency rating of 18–22%.

The potential savings you will be able to make through using solar panels have been extensively covered in our guide “How Much Do Solar Panels Save.” Here is a list of the different solar panel varieties and their associated efficiency percentages.

Monocrystalline Solar Panels: 18–22% Average Efficiency

Monocrystalline panels have been created using a single sheet of silicon crystal. As their surface features no natural breaks, they are the most efficient panel variety when it comes to photon ray absorption.

Widely regarded as the current solar industry leader, mono panels are able to achieve the (currently) peak efficiency benchmark of 22% when installed optimally and placed in an ideal location. Monocrystalline panels are also the most expensive variety of solar panel available.

Polycrystalline Solar Panels: 13–16% Average Efficiency

Polycrystalline solar panels are created using several pieces of silicon that are fused together to create one individual sheet. As these panels have not been formed using one singular sheet of silicon, they contain natural breaks in their structure.

This means that they are not able to absorb photon rays to the same extent that monocrystalline panels are. Instead, they come in second place to mono panels with an efficiency rating of 13–16%. As polycrystalline panels carry a lower efficiency rating than that of monocrystalline panels, they also carry a lower price tag in turn.

Thin Film/Flexible Solar Panels: 7–14% Average Efficiency

The most inefficient solar panels available, thin film panels, are made out of a conductive silicon material that is wafer thin and highly flexible. As the material used is not anywhere near as substantial and absorbent as a solid silicon crystal sheet, these panels are only able to achieve a total efficiency range of between 7–14%.

The benefit of thin film panels is that they can be placed almost anywhere with ease. This includes awkward locations like curved walls or even on vehicles. They are also the cheapest variety of solar panel available.

Solar Panel Efficiency Chart

Here is a list of the top ten brands currently producing the most efficient solar panels available for purchase.

Brand and model	Efficiency rating	Power capacity (in watts)
1. Maxeon 3 by SunPower®	22.6	400
2. Neon R by LG	21.7	375
3. Alpha Series by REC	21.7	380
4. Solar Hi-Mo X by LONGi	20.3	355
5. Q.Peak Duo G6+ by Qcells	20.1	350
6. Solar Cheeta HC by Jinko	19.6	330
7. Honey Splitmax by Trina Solar	19.6	330
8. JAM60S10 by JA Solar	19.6	330
9. Twin Plus by Phono Solar	19.6	330
10. WSP-MX by Winaico	19.4	340

Factors That Affect Solar Panel Efficiency

There are numerous factors that affect solar panel efficiency. We are going to try and cover them all in this section so that you stand the best chance possible of getting the most out of your solar system.

Why Solar Panel Efficiency Is Low

As with many pieces of technology, the technology itself is not always to blame when you are not getting the results that you would expect. Instead, it could be the way that you are using it. Solar panels are no different.

Your panels must be professionally installed.
Ensure that you take action to avoid snow and ice build-up.
Clean your panels regularly.
Make certain that your panels are placed in an ideal location and at an ideal angle.
Factor the number of peak daylight hours per day in your area into your energy calculations.

Here are the main areas to consider when it comes to solar panel efficiency.

What Time of Day Are Solar Panels Most Efficient? How Low-Daylight Hours Can Impact Solar Efficiency

Solar panels definitely function better at certain times of the day.

Solar panels are at their most efficient between 11:00 AM and 4:00 PM.
Before 11:00 AM, the sun has not fully risen. Therefore, your panels are not going to be able to absorb the peak amount of photon rays.
After 4:00 PM, the sun begins to set, meaning that your panels will not be able to access the peak amount of photon rays again.

As such, you should consider the average number of peak daylight hours in your area per year as this directly impacts solar panel efficiency. We previously covered this subject in a comprehensive chart in our guide titled “How Many Solar Panels Do You Need?”

At What Temperature Do Solar Panels Work Best? Why It Is Important to Know Your Optimal Operating Temperature

One of the reasons why some people struggle to get the most out of their solar panels is that their panels are situated in such a way that they are not able to operate at their optimal operating temperature.

Consider the following important points.

Solar panels are at their most efficient when they operate at a temperature of 25 degrees Celsius (77 degrees Fahrenheit).
When the temperature of your panels elevates beyond this point, it negatively affects the electrons inside the panels and diminishes their ability to be able to produce energy.

At 25 degrees Celsius or just below, the electrons inside your solar panels rest in something known as a ground state. At this state, they are stable and therefore able to produce energy seamlessly.

When higher temperatures are introduced, this agitates the electrons and leads to them entering something known as the excited state. The higher the temperature, the more excited they become.

When the electrons are in this excited state, they become unstable and are not capable of producing energy seamlessly. In other words, the hotter the panels become after 25 degrees and above, the less energy they are going to be capable of producing.

The average annual temperature in your area will therefore impact your solar panel efficiency. Solar panel operating temperature capacities are also known as solar panel coefficiency ratings. The efficiency of your panels will drop by 0.20 to 0.50 percent per degree Celsius past 25 degrees depending on your make and model.

Solar Panels in Cold Areas: Do Solar Panels Work Better in the Cold?

There is no conclusive evidence to state that solar panels are able to operate better in the cold. Solar panels are likely to operate just as efficiently in cold weather provided that there is ample sunlight available.

It is only when temperatures elevate past 25 degrees Celsius, as previously mentioned, that issues begin to arise in relation to solar panel power output capacity. Before this point, they are able to produce energy to optimum levels based on the amount of available sunlight in your area.

What Happens if There Is Snow on Solar Panels?

When your solar panels are covered in snow, this means that their surface has been obstructed. When this happens, your panels are not going to be able to access the maximum amount of sunlight.

Solar panels can still function when they have a light layer of snow on them, though their efficiency is likely to be diminished.
Anything other than a light smattering of snow can lead to your panels not being able to absorb photon rays whatsoever.

Whether your panels can function with snow on them depends on how thick the build-up is. Cold temperatures do not have a negative impact on solar panel performance, but obstruction does.

Does Ice Affect Solar Panels?

Interestingly, ice does not always affect solar panel efficiency in the same way that snow does. This is because ice can freeze in an almost transparent state.

The thinner the ice layers over the surface of your solar panels are, the less they will interfere with your panels’ capacity to absorb photon rays.
Thick ice can severely reduce solar panel efficiency and can even prevent them from functioning in some cases.

This is why it is important to perform regular maintenance via the use of specialized solutions to stop any severe build-up from occurring if you live in an area that is prone to severe cold spells.

Why Is Antifreeze Used in Solar Panels? Can This Take Care of Snow and Ice Build-Up?

If you are in an area that is prone to incredibly cold weather, you will be pleased to know that some solar panel systems come with built-in antifreeze technology.

Antifreeze systems can stop ice and snow from building up on the surface of your panels.
This can be the difference between solar panels being a viable energy solution in some areas or not at all.
The additional cost of antifreeze systems is well worth the return in guaranteed efficiency throughout the year, regardless of the weather.

Do not just think of the upfront cost when it comes to antifreeze systems. Think about the long-term energy return.

Solar Panel Cleanliness: Does Cleaning Solar Panels Improve Performance?

If you have not cleaned your panels in a while, then consider these facts.

In order for solar panels to be able to access photon rays to the maximum extent, the surface must be as clear as possible.
Your panel efficiency may decrease by 1% per month for every month that they are not cleaned thoroughly.

As you can see, solar panel cleanliness really does matter.

Do Solar Panels Work During Rain? Can I Rely Purely on Rainfall to Clean Them?

Rainfall will not be enough to keep your solar panels optimally clean and capable of producing energy in line with their maximum efficiency standards.

Rainwater does not clean solar panels thoroughly.
Every month that your panels are cleaned purely by rainwater alone, they will lose roughly 1% in overall efficiency.
Solar panels are still capable of producing energy during periods of rainfall, but the amount of energy can be reduced by storm clouds.

The only way to guarantee that your solar panel surface remains as absorbent of photons as possible (and therefore capable of taking in the maximum amount of photon ray energy for redistribution as electricity) is to clean it by hand using specialist tools and solutions.

How Often Should I Clean My Solar Panels?

To keep your solar panels as clean as possible, you should take the following steps.

Aim to clean your panels at least once per year, ideally twice.
Use a monitoring system to try and gauge when your panels may have gathered too much excess dirt. As there is an average of a 1% drop in efficiency per every month that your panels are not cleaned, you should be able to tell when your energy output has diminished to a point where intervention is necessary through using solar monitoring.

Cleaning once every 6 months or even quarterly is ideal if you are able to do it yourself without paying for a cleaning company.

Do I Need to Turn Off Solar Panels to Clean Them?

In order to safely and effectively clean your solar panels, you will definitely need to take safety measures.

Completely turn them off.
Enlist the help of someone with experience in this area if you are unsure about how to do this.

You may also be able to find out all of the information you require about powering your system down by watching internet tutorials. Your safety will be at risk if you try to clean the system while it is still switched on.

Do Solar Panels Lose Efficiency Over Time? When Should You Replace Solar Panels?

Unfortunately, solar panels do lose efficiency over time.

On average, solar panels lose roughly 1% efficiency per year of their life span.
After 20–25 years, most solar panel systems will need to be replaced as they can only produce 70%–80% of their original capacity.

When you should consider replacing them depends entirely on how long they are going to remain a financially viable energy solution for you.

There are people who will still be able to cover 100% of their home’s energy requirements with panels that are operating at 90% of their original efficiency standard. Some may even find 80% acceptable when the panels are 20 or more years old.

On balance, others will be running their systems so tightly that they need every percentage point of their panel efficiency to be able to cover 100% of their energy needs.

Solar Panel Efficiency Over Time Chart

A chart showing the loss of solar panel efficiency over time can be found here. Depending on the make and model of your solar panels, they may lose more or less than the predicted 1% efficiency drop per year.

How Can We Increase the Efficiency of Solar Panels?

In this section we are going to discuss all of the ways that you can make your solar panels as efficient as possible. It all starts with the initial calculations prior to installing your solar panels. If you do not calculate your energy requirements and the efficiency of your solar panels effectively, then they are not going to be able to adequately cover your energy requirements.

Solar Panel Efficiency Formula

In order to figure out how efficient your solar panels are, you will need to make use of a solar panel efficiency formula.

The information you will need to be able to work with this formula is as follows.

Find out what the unit’s maximum power capacity is.
Measure the length and height of your solar panel. Then, take note of the dimensions.
Divide your solar panel’s power capacity into the maximum area of your panel. This will give you a capacity rating in watts per square meter.
Find out what the solar irradiance value under standard test conditions for your panel is. This is usually available in the manufacturer’s guide.

Once you have all of this information, you will then be able to calculate the overall efficiency of your solar panel. In order to do so, simply divide the power per unit value (the watts per square meter capacity rating) by the irradiance value to get your panel’s total efficiency rating.

Solar Cell Efficiency: The Importance of Getting the Installation Process Right

A large part of your solar panel efficiency capacity is all going to be down to the installation process. When solar panels are not installed appropriately, you will lose a considerable amount of energy and waste thousands of dollars.

Here are some important factors to consider.

If your system is not installed by a qualified professional, then all of the individual components might not seamlessly communicate with each other, thus leading to an enormous energy drain.
Direction plays an enormous part in the efficiency of your solar panels. They should ideally be facing due south and angled at roughly 45 degrees in order to be able to maximally absorb incoming photon rays from the sun.
The number of peak daylight hours available in your area plays an enormous part in determining how much potential power your solar panels may be able to generate. Therefore, pre-installation surveys are especially important.

Let’s dive into these individual areas in more detail to explain how they can negatively impact the efficiency of your solar panels.

Qualified Solar Panel Installation

Even though there are DIY guides like the incredibly popular Backyard Revolution that offer a comprehensive, step-by-step solution for those who want to create their own solar panel systems, the easiest way to guarantee that you are able to achieve peak efficiency with your system is to have it installed by a qualified professional.

There is a great deal to consider when it comes to installing solar panels, which in turn means that there is a great deal to possibly get wrong.
Using a qualified and experienced professional means that from day one, the stage is going to be set for you to access 100% of the efficiency you are expecting from your chosen solar system.
100% efficiency capacity means you will make 100% of the savings you are expecting from your panels too.

Consider the long-term savings more than the upfront costs when going solar, and remember that you can lease your panels if the initial costs are too high for you at the moment.

Solar Panel Placement

As part of your solar system installation, you will need to ensure that your panels are placed at the optimal south-facing, 45-degree tilt angle in order for them to be able to maximally access the sun’s photon rays.

We previously covered this topic in our guide “How Many Solar Panels Do I Need.” If you are performing a self-installation, then getting this part wrong could quite literally lose you thousands of dollars.

You can find a comprehensive table in this guide that shows the difference in efficiency achieved when solar panels are placed at varying angles and directions. Provided you get this part right, then your panels will be able to operate at optimum efficiency.

The Number of Peak Daylight Hours in Your Area

Depending on where you live in the world, you are going to have access to less or more peak daylight hours than others. This will significantly impact your solar panels’ ability to access photon rays.

The less peak daylight hours available, the less energy that your panels will be able to produce.
With less daylight hours, your panels will be able to cover less of your household energy requirements. In turn, you will then have to spend more money on your energy bills.

You can find a table here that shows the number of peak daylight hours in each American state. Some locations will always benefit from using solar technology far more than others.

Solar Monitoring: The Key to Maximum Efficiency

Using a solar monitoring system will allow you to squeeze every last drop of energy out of your solar panels and maximize their efficiency.

Monitoring systems do not just tell you how much energy your system is producing, but they also tell you when this energy is not being produced.
Monitoring allows you to spot energy bleeds and isolate damaged components long before you lose a significant amount of energy and therefore money.

By using a sophisticated analysis process, you can quickly find and resolve any system issues before they get worse and lead to long-term losses.

Properly Maintaining Your Solar Panels for Maximum Efficiency

Clean panels produce much more energy than dirty panels. Regardless of how you choose to clean your system (whether it is with your own hands or through a company), the energy returns you will see as a result of keeping them clean far outweigh the financial outlay of having them cleaned or buying the products required to clean them.

To avoid losing roughly 1% efficiency per every month that they remain dirty, always ensure that you have your system cleaned ideally quarterly but at a minimum once per year.
Through the use of a monitoring system, you can spot issues before they become a serious problem.
Regular servicing will allow you to get a full analysis of every component to guarantee that everything is working as it should be.
Annual solar system inspections are also a great idea especially when you combine them with an annual cleaning.

The combination of the above maintenance along with the use of a monitoring system will always be the best way to guarantee optimum efficiency.

Installing Reflective Solar Mirrors

Even though they are still quite expensive, solar mirror reflectors are a proven way to increase the efficiency of your solar panels without having to take up further space.

Solar mirrors reflect sunlight back onto the panels, meaning that they are essentially able to catch any photon rays that they may have initially missed with the first absorption cycle.
During winter months, solar mirrors have been shown to improve solar panel efficiency by roughly 13%.
During the summer months, this efficiency increase elevates to 20% and even 30%.

If you have the resources to be able to do so, then installing solar mirror reflectors is a great way to achieve a higher efficiency rating and reach combined ratings of almost 50%, which matches solar panel models that are currently only at the concept stage.

Solar Panel Efficiency FAQ

In this section, we are going to answer the most frequently asked questions about solar panel efficiency.

Q: What types of solar panels are most efficient?

A: It is commonly accepted that the most efficient solar panel variety is the monocrystalline solar panel. It carries a maximum efficiency rating of between 22%–26%, meaning that it can produce more energy than any other solar panel type currently in commercial circulation.

Q: What are the top 10 most efficient solar panels?

A: Here are the top 10 most efficient solar panels (in order).

SunPower Maxeon 3
LG Neon R
REC Alpha
FuturaSun FU M Zebra
Panasonic EverVolt
Trina Solar Vertex S
Jinko Solar Tiger Pro 6R13
Q Cells Q.Peak DUO G9
Winaico WST-375MG
Longi Solar Hi-Mo 4

Q: Do solar panels lose efficiency over time? Can you increase their efficiency?

A: Unfortunately, solar panels do lose efficiency over time. Solar panels lose 1% efficiency for every year of their life span. This means that by the time they reach the typical 20–25-year life cycle, they have lost roughly 20% or more of their overall efficiency.

Q: Can solar panels be 100% efficient?

A: Currently, commercially available solar panels can only achieve a maximum of 22%–26% efficiency. This is through the use of monocrystalline silicon cells.

There are alternative forms of solar technology at the concept stage that have achieved efficiency ratings of almost 50%. These models may soon set the new standard for commercially available efficiency.

Q: What are the most efficient solar panels in 2021?

A: The most efficient solar panels available in 2021 can be found in the top 10 most efficient solar panel list mentioned previously in this guide.

Q: What is the highest solar panel efficiency in 2021?

A: Currently, the highest commercially available efficiency standard available for solar panels is between 22%–26%.

Q: Why is solar panel efficiency low?

A: Generally speaking, the reason why you will need several solar panels in order to be able to meet the energy requirements of your home is that solar power is a passive form of power production.

Whereas traditional power draws directly from the grid, solar power instead relies on the absorption of photon rays. As the most advanced commercially available solar panels can only achieve a maximum absorption rate of roughly 22%, this means that the efficiency of solar power is currently much lower than that of grid power, which is virtually 100%.

Q: How can you increase the efficiency of a solar panel?

A: In order to increase the efficiency of a solar panel, you can carry out the following steps.

Perform regular quarterly cleaning of your solar panel system.
Have an annual solar system inspection to determine if there are any issues with your system that might be negatively impacting its efficiency.
Use a solar monitoring system to detect any potential energy bleeds and remedy them before large amounts of power are lost.

All of the above will help you to improve the efficiency of your solar panel system.

Q: What time of day are solar panels most efficient?

A: Solar panels are most efficient between 11:00 AM to 4:00 PM as this is typically when the most sunlight is available per day.

Q: What time do solar panels start working?

A: Solar panels will start working as soon as the sun begins to rise in the morning, but they usually begin to work optimally at 11:00 AM in the morning and their efficiency rapidly declines from 4:00 PM onwards.

Q: Do solar panels drain batteries at night?

A: Even though solar panels do draw from batteries at night, they do not excessively drain them. The excess power that the panels produce during the day is largely what allows them to sustain your household appliances and lighting at night through energy saved in charged batteries.

Q: Can mirrors increase solar panel output?

A: Reflective mirrors have been known to increase solar power output and therefore overall efficiency by as much as 20%–30% depending on the season. In certain areas of the world, this could make a considerable difference and lead to enormous long-term cost savings.

Q: How many solar panels would it take to power a house?

A: It is almost impossible to give a precise figure that could cover any size of home because all houses have different energy requirements, but the majority of houses could be powered by a system that has anywhere from 17 to 42 solar panels depending on their power output capacity.

Q: Do solar panels last forever?

A: Solar panels do not last forever. Generally speaking, solar panels will be able to produce enough energy to cover the requirements of an average household for around 25 years.

Once they reach 25 years, their efficiency drops by roughly 20%. They are still capable of producing power to roughly 80% of their original capacity, but at 80% or less, the panels will struggle to be able to meet 100% of the energy requirements of a house.

Q: Do solar panels work with moonlight?

A: Solar panels do not work with moonlight. Even though the moon emits a natural glow, it does not produce any photon rays. As photon rays are critical for a solar panel’s functionality, this means that the moon cannot provide any useful “fuel” through which solar panels are able to produce energy.

Q: Do solar panels work during rain?

A: Solar panels can still work in rain. As long as there is some sunlight available, the panels will still be able to access photon rays.

Q: Do solar panels work without direct sunlight?

A: Solar panels do still work without direct sunlight. Even though they are at their most efficient when they receive direct, abundant sunlight. They can still operate via reflective sunlight too.

Q: Do solar panels work better when it is hotter?

A: No, they do not. Solar panels do not actually require heat in order to operate. Provided they are able to access photon rays, then they have everything they need in order to produce energy.

On the contrary, their efficiency can actually decline when they get too hot. Past temperatures of 25 degrees and above, solar panels are able to produce less and less energy as a result of their internal composition being destabilized.

Q: Why do solar panels work better in the cold?

A: Interestingly, solar panels actually function better in cooler temperatures because their internal electrons are stable, meaning that the panel is able to produce a more constant and reliable stream of energy.

Conclusion

It is vital to go for the most efficient panels possible when you decide to go solar. Any of the items in our top ten list will prove to be completely viable for achieving enormous long-term cost savings as will several cheaper options, which have been covered in our guide on cheap solar panels.

While budget is an all-important factor, it is also vital to prioritize sustainability and pay slightly more (if possible) to guarantee that your solar future is a bright one. Professional installation and proper maintenance will ensure that the most efficient solar panel models on the market will always maintain their high-energy production standards.

Monocrystalline panels are typically regarded as being the industry leader when it comes to efficiency, but do not rule out the other options. Remember, the priority is to cover your energy needs regardless of what they are.

If you can do this through using cheaper and less efficient solar panel varieties, then there is absolutely nothing wrong with doing this. 22%–26% is the current industry benchmark for maximum efficiency. The closer you can get to achieving this figure, the better.

Once you have found the right panels for you based on their cost and efficiency and have successfully installed them based on the ideal direction and tilt angle, then it is time to start making some considerable savings.

Efficient solar panel models that have been correctly installed are not just efficient at absorbing photon rays. They are also efficient at saving you a great deal of money too. We hope that you have a happy and efficient solar future.