What is Solar Panel Efficiency? A Guide to Maximum Solar Output
Solar panel efficiency is a key yardstick for judging a panel’s ability to convert solar photons into power. The greater the efficiency of a solar panel, the more electricity it will generate per unit of incident light. You must consider efficiency when buying a particular solar panel model.
Solar panel efficiency is the percentage of solar energy incident on a solar panel which is converted into solar electricity. For example, if a solar panel has an efficiency of 20%, it means that if 100 units of solar energy are incident on the solar panel, 20 units of solar energy are converted into solar electricity.
A higher solar efficiency offers several advantages such as it can generate more energy. That means, you will have to install less number of panels to get the required power output. It ensures enhanced space efficiency, higher electricity generation, and increased savings. However, highly efficient solar panels come at increased prices.
Solar Power Efficiency According to Panel Type
Different types of solar panels have different efficiencies. Here’s a breakdown of solar panel efficiency by panel type:
| Type of Solar Panel | Efficiency |
| Polycrystalline | 12% to 17% |
| Monocrystalline | 17% to 22% |
| Mono PERC (Monofacial) | 20% to 21% |
| Mono PERC (Bifacial) | 20% to 21% and extra up to 15% due to bifacial facility |
| TOPCon (Monofacial) | 21% to 23% |
| TOPCon (Bifacial) | 21% to 23% and extra up to 15% due to bifacial facility |
How to Calculate Solar Panel Efficiency?
The following formula is used for calculating the efficiency of solar panels:
Efficiency (%) = Power Output (Watts)/(1000 Watts/m2 x Area of the solar panel (m2)) X 100
Follow these steps to calculate the efficiency of a solar panel:
Step 1: Determine Power Output
Find the power output of your solar panel by checking its specification sheet.
Power output is measured in laboratory conditions of 25°C and solar intensity of 1000 W/m2.
Step 2: Calculate the Panel’s Area
Multiply the length and breadth of the solar panel to find its area. Dimensions of a solar panel can be found in the specification sheet.
Step 3: Use the Formula by Entering the Data
Enter the required data into the formula for calculating the efficiency of solar panels.
Example of How to Use the Solar Efficiency Formula
Suppose you have a solar panel with a power output of 550 W. Its dimensions are 2.45 m and 1.13 m. Then the area of the solar panel is 2.45 x 1.13 m2 = 2.77 m2.
Efficiency (%) = 550/(1000 x 2.77) x 100 = 19.85%
Why Is High Solar Panel Efficiency Important?
Here’s why the high efficiency of solar modules is important:
- Improve Space Efficiency
The lower the efficiency of solar panels, the more area a solar system needs to generate a certain amount of electricity.
In other words, for a fixed solar output, the efficiency of solar panels is inversely proportional to the solar system’s space requirement. Therefore, to minimise the area your solar system occupies, you must install highly efficient solar panels.
On the other hand, if you don’t face any space constraints, you can install panels with a lower efficiency. Such panels are likely to be cheaper than the more efficient ones.
- Increased Savings
The main reason why you would install a solar system at your home is to save on your electricity bills. With high solar system efficiency, you can maximise your savings and return on investment.
- Less Power Loss due to High Temperature
The productivity of solar panels gets less as they get hot. If you have a solar panel with a higher efficiency, the power loss will be less compared to solar panels with a lower efficiency.
How To Maximize Solar Panel Efficiency
Here are the steps you can follow to maximise solar panel efficiency:
- Let Experts Install Your Solar System
You must hire an expert vendor to install your solar system. They can help you in selecting the right components, the right angle of installation, and the right mounting structure.
If you want to get in touch with the best solar vendors in India, you can use free solar quotation service from Das Energie. Our vendors follow industry-leading practices for installing solar systems.
- Regularly Clean Your Solar Panels
The productivity of your solar panels can decline by 30% if they are not cleaned for 6 months. It is important to clean them at least once a month to maintain their efficiency. You can read our blog on solar panel cleaning to learn about the best solar panel cleaning practices.
- Properly Maintain Your Solar Panels
Frequent check-ups of the solar system are vital to ensure its long life. From preventing any damage to correcting problems in the system, there are several aspects of solar panel maintenance. You can read our blog to learn more about them.
- Solar Panel Orientation
Your solar system must be properly oriented to convert the maximum amount of sunlight into electricity. According to the latitude and longitude of the place, the solar panel orientation must be decided.
- Don’t Install in a Shaded Area
The solar power panel efficiency is drastically reduced when a shadow covers the solar panels. So always install your solar system in a place where there is no shadow.
15 Factors Which Affect Solar Panel Efficiency
Here are the factors which affect solar array efficiency:
1. Type of Solar Panel
The technology of the solar cells in the solar panels influences the efficiency of the solar panels. TOPCon solar panels have the highest efficiency of 21% to 23%, followed by mono PERC solar panels with an efficiency of 20% to 21%. Naturally, the efficiency of bifacial solar panels is greater than that of monofacial solar panels.
Another thing to remember is that most solar panels don’t produce electricity when a shadow covers them. The only exception to this is solar panels with half-cut solar cells. For example, even if a shadow partially covers a mono PERC half-cut solar panel, the half which is not covered by the shadow will continue to produce solar electricity.
2. Shadow
For maximum solar power efficiency, you must prevent shadows from falling on your solar panels. If a shadow covers even one solar panel partially, it can drastically reduce the efficiency and output of your solar system. Trees and buildings are common obstacles blocking the path of sunlight, thus leading to a decline in power generation.
Hold thorough consultations with your solar vendors to decide which location is best suited to install your solar system.
Das Energie is connected with the best solar vendors in India. You can employ them for a seamless solar system installation.
3. Pitch of the Roof
The angle at which the sunlight strikes the solar panels is critical for the efficiency of solar modules. You have to install the solar panels per your roof’s pitch. In case you don’t have a flat roof, here’s how to measure the pitch of your roof:
Video Credit: BoutenkoFilms
4. Positioning and Angle of Solar Panel Installation
Sunlight must fall perpendicularly on the solar panels for maximum solar panel efficiency. The best solar panel direction and angle depend on the location of your solar system.
Depending on the latitude and longitude of the place where the solar system has to be installed, the solar installer will determine the ideal north-south and east-west orientation of the solar panels.
Large-scale solar installations use solar trackers so that the solar panels follow the movement of the sun. It ensures that sunlight falls at 90 degrees on the solar panels.
5. Dust and Pollution
Dust, dirt, and grime covering the solar panels can drastically reduce solar system efficiency. In a dusty country like India, it is important to clean the solar panels at least once every month. You can purchase a solar AMC to have a professional to clean your solar panels regularly.
6. Wavelength
The wavelength of sunlight determines its energy. Sunlight itself is made of photons. When sunlight falls on the solar panels, the photons with the right amount of energy dislocate electrons and set the electricity flowing through the circuit. The energy of other photos turns into heat.
7. Reflection
The solar cells and the glass surface of the solar panels reflect some of the sunlight which falls on them. It decreases the solar power panel output. That’s why anti-reflective coating is used on the solar cells to increase the solar panel efficiency. This is because the coating help the panel absorb more sunlight than they reflect.
8. Temperature
The temperature coefficient of a solar panel is a percentage which shows the decline in the output of a solar panel with an increase in temperature. The temperature increase is usually measured from 25°C.
As a solar panel gets hot, its efficiency decreases. Cold to moderate conditions are best for the efficiency of solar panels.
9. Recombination
Two major “charge carriers” in a semiconductor are electrons and holes. If electrons and holes recombine with each other, they will play no role in generating electricity, thus reducing the solar system’s efficiency. Recombination can also happen when electrons and holes encounter any impurities in the solar cell.
10. Cloudy Weather
Solar array output is directly proportional to the amount of sunlight falling on the solar panels. In cloudy weather, sunlight is obstructed by the clouds. Thus the output of a solar system is reduced in cloudy weather.
11. Wind
Wind has a cooling effect on the solar panels, thus improving their efficiency. Although an environmental phenomenon, wind can also remove clouds from the path of sunlight, thus increasing solar system output. But you must also ensure that the solar panels are perfectly installed on the mounting structure so that solar panels don’t fall off.
You can read our blog to learn about the different types of mounting structures for solar systems.
12. Snow
A little bit of snow won’t have much of an impact on solar system output. However, too much snow can hinder the solar cells from receiving sunlight. Too much snow can create pressure resulting in microcracks.
13. Humidity
Humidity can lower the efficiency of solar panels. Water droplets on solar panels can reflect and refract sunlight, reducing the sunlight falling on the solar panels. Hot, humid weather can degrade the solar panels as well.
14. Chemical Residue
Harsh chemicals can damage the solar panels and their anti-reflective coating, reducing the solar panel efficiency over time.
15. UV Degradation
Exposure to UV radiation destroys silicon and passivation layers in a solar cell. It reduces the power output of the solar panels and harms their durability.
Module Efficiency vs System Efficiency
You need to distinguish between solar module efficiency and the efficiency of the entire solar system. Solar module efficiency refers to the efficiency of a single solar panel whereas solar system efficiency refers to the efficiency of the total solar system.
When a solar panel generates electricity, some of the power is lost while sending it to the inverter. Further, there is some loss of electricity as the electricity is sent from the inverter to the appliances.
Thus, the efficiency of individual solar panels is greater than that of an entire solar system. If the efficiency of the solar panels is 20% to 23%, the efficiency of the solar system could be around 18% to 19%.
Do Solar Panels Lose Efficiency Over Time?
Yes, solar panels lose their efficiency over time. You can check the data sheet of the solar panel while purchasing it to find out how much it will degrade with time. It is usually mentioned under the section “Performance Warranty” or “Power Output Warranty”.
In the 1st year, the solar panel efficiency degrades by 1-2%, thereafter between the 2nd and 30th years, it declines by 0.3-0.5% annually.
Do Solar Panels Work In Cold Weather?
The efficiency of a solar panel is related to the amount and intensity of sunlight that is available and the temperature of the solar panels.
The temperature coefficient shows how the efficiency of a solar panel falls with an increase in temperature. Therefore, in cold weather, a solar panel will be more efficient compared to in hot weather. But along with cold weather, if the day is cloudy or the intensity of the sunlight is low, it will naturally result in a lower intensity.
Do Solar Panels Work In The Rain?
The cloudy weather during the rainy season hinders the path of sunlight. It reduces the amount and intensity of sunlight reaching the solar panels, thus lowering their efficiency.
The only positive impact of rain is the cleaning up of the solar panels. If too much dust has accumulated on the solar panels, the rain can clean up the surface, thus helping the solar panel generate more electricity in less cloudy days.
Common Misconceptions About Solar Panel Efficiency
Here are some of the misconceptions which people have about solar panel efficiency:
Misconception 1: Solar Panel Efficiency Equals Product Quality
Fact Check: Solar panel efficiency is only one of the indicators of the overall quality of the product. You need to judge a solar panel based on your needs. For example, if you have a lot of space and your power requirements are small, you could buy cheaper solar panels with a lower efficiency for your solar system.
Factors you must consider while considering a solar panel’s quality include its capacity, the type of solar cells in the panel, and its dimensions.
Misconception 2: Solar Systems Work Only in Sunny Climate
Fact Check: A solar system will generate electricity if sunlight falls on the solar panels. Solar panels are more efficient in cold temperatures. Even during the winter and rainy seasons, if sunlight is available and falls on the solar panels, the solar system will produce electricity.
Misconception 3: Solar Panels Don’t Need Regular Cleaning
Fact Check: The cleanliness requirement of solar panels depends on the solar system’s location. In a dusty country like India, solar panels need to be regularly cleaned or else dust, grime, bird droppings, and leaves will soon lead to a decline in the solar system’s output. It is best to clean the solar panels once every month.
TOPCon and mono-PERC solar panels have the highest solar panel efficiency. You must compare the data sheets of different solar panels to understand their pros and cons. From reducing the loss of electricity due to high temperatures to improving the solar system’s space efficiency, there are several advantages of high solar panel efficiency.
Frequently Asked Questions
Solar array efficiency is the percentage of electricity incident on a solar panel which is converted into electricity.
Solar trackers follow the movement of the sun to ensure that sunlight falls perpendicularly on the solar panels. This maximises the power output of the solar system.
The efficiency of solar modules depends on the intensity of the sunlight and the technology of the solar panels. If the availability of sunlight is low due to clouds in the sky, then the productivity of the panels also falls.
You must clean the solar panels at least once a month to retain the best solar power panel efficiency.
