Solar Panel Efficiency
Solar panels consist of modules or photovoltaic (PV) cells. You can measure the efficiency of a PV cell based on the percentage of light energy it converts into electricity. Solar cell efficiency is the ability of a panel to capture energy from photons or light particles. When light hits a solar panel, it releases electrons that start moving and create an electrical current.
For example, a solar panel with a 20% efficiency can convert 20% of sunlight into usable energy. Most commercially available solar panels have an efficiency of less than 23%, with an average range of 15% to 20%. Canadian Solar currently tops the industry with 22.8% efficient panels.
Module Efficiency vs. System Efficiency
Solar panels are good at turning sunlight into electricity, but there are still some energy losses when the electricity travels through the wiring in the system. Also, the electricity needs to be changed from what solar panels make (called direct current, or DC) into what our homes use (called alternating current, or AC). This changes with an inverter. There are usually small losses of energy during this process.
Because of these losses, the efficiency of each solar panel will always be higher than the efficiency of the whole system. For example, if the solar panels on a house are 22% efficient on their own, the overall efficiency of the whole system might be around 19%.
Common Misconceptions About Solar Panel Performance
A common misconception is that solar panel performance equates to product quality. Solar panel performance is just one of the protective features. Such as power rating and module dimensions, and you can find high-quality panels of all performance levels.
The main factor determining efficiency is the material of the solar panel:
- Monocrystalline silicon panels have a typical efficiency of over 20%.
- The typical efficiency of polycrystalline silicon panels is less than 20%.
- Thin-film panels are generally the least efficient, but newer materials such as perovskite can match the efficiency of silicon cells.
Monocrystalline solar panels capture more light from the sun and generate more electricity. They are great for generating a lot of electricity from a small space, but they are more expensive. If you have enough space for your PV system, you Can also use cheaper Solar panels.
Why Is Solar Panel Efficiency Important?
Although high-efficiency solar panels are more expensive, they offer several advantages. Plus, your electricity savings from going solar can help you recover the higher upfront cost over time. Here are a few benefits of high-efficiency solar panels:
Use Space More Effectively
Since high-efficiency modules convert a higher rate of sunlight into electricity, they allow you to use roof space more effectively. For example, compared to 10% efficient panels, 20% efficient panels can generate twice as much electricity per square foot. In other words, high-efficiency solar panels produce more energy using fewer panels. If the area available for your PV array is limited, you can achieve maximum control output with monocrystalline solar panels.
Offer Higher Energy Savings
Monocrystalline panels have a higher efficiency and wattage than polycrystalline panels of the same size. For example, when comparing 60-cell solar modules, you might find a 300-watt (W) poly panel versus a 370-W mono panel. Here’s an example of how solar panel wattage can impact your system size and energy savings:
- If you have space for 20 panels on your roof, you can reach a total system wattage of 6 kilowatts (kW) with polycrystalline panels and 7.4 kW with monocrystalline panels.
- With favorable sunlight, the 6 kW system can generate over 9,000 kWh of usable electricity each year, but a 7.4 kW system can generate over 11,000 kWh.
- Assuming you pay an electric tariff of 16 cents per kilowatt-hour (kWh), the 6 kW system can save around $1,440 in annual electricity bills, but the 7.2 kW system saves around $1,760.
The average cost of solar panels is $2.85 per watt, according to our March 2023 survey of 1,000 homeowners with installed solar. Since monocrystalline panels have a higher wattage, they also cost more than polycrystalline panels. In any case, the price difference is minimal when you compare both panel types in terms of cost per watt.
Less Impact from High Temperatures
All solar panels suffer a small loss in wattage as they heat up. This effect is temporary — panels recover the lost productivity once they cool down. In any case, when you constantly expose solar panels to hot weather, the loss of production can add up over time. As a result, hot temperatures can result in a 10% to 25% decrease in solar panel efficiency.
Solar panels have a metric called the temperature coefficient, which describes the negative effect of heat. For example, a panel with a coefficient of -0.40% per Celsius degree will lose 8% productivity with a temperature rise of 20°C. On average, monocrystalline panels have lower temperature coefficients than polycrystalline panels, which means they are less affected by heat. This is a major advantage in warm regions where hot temperatures can impact solar panel performance over time.
Qualify for Higher Solar Incentives
Many solar benefit programs calculate financial incentives by the per-watt capacity of your solar system. Since high-efficiency panels have a higher wattage, they can qualify for higher incentive amounts. However, this does not apply to incentive programs with fixed rebates.
The federal solar tax credit is a nationwide incentive that allows you to claim 30% of your solar system costs as an assessment credit for the year you install panels. Since monocrystalline panels cost more, your total system cost will likely be higher than if you used polycrystalline panels. As a result, you will see a higher tax incentive per panel.
How To Maximize Solar Panel Efficiency
There are a few ways to maximize the conversion efficiency of your solar system.
Get a Professional Installation
Professional installers properly wire your solar panels according to the manufacturer’s instructions. If not wired correctly, solar panels can have voltage and current issues that negatively impact their durability and productivity.
The best solar panels come with a 25-year warranty, but most companies only offer this benefit with a professional installation. In other words, you will void your warranty if you attempt a DIY installation. A warranty can conserve the overall efficiency of your solar energy system by replacing defective panels for free.
Ensure Your Panels Are Free of Debris
Photovoltaic cells can only generate electricity when light reaches their surface. So if dust and other particles accumulate on the surface of your panels, less sunlight reaches the PV cells, and electricity generation drops. The cleaning needs of your solar array depend on site conditions, but many solar installers recommend cleaning your panels at least twice a year.
Several manufacturers are developing ceramic coatings for solar panels to reduce the accumulation of dust and other particles. These products are still relatively new but have promising applications.
Clean Your Solar Panels Properly
Cleaning your solar panels is important, but the wrong tools and methods can shorten their lifespan. Here are general guidelines to keep in mind:
- Avoid using abrasive tools like hard brushes, roof rakes, and chemical agents.
- Soft brushes and squeegees are ideal for cleaning solar panels since they don’t cause scratches.
- You can also wash your solar panels with a hose, but not when your panels are hot, as the drastic temperature change can cause cracks.
Solar panels tend to lose efficiency when damaged, and in worst-case scenarios, may stop working completely. For the most part, a solar panel warranty will not cover damage due to incorrect cleaning methods.
Avoid Installing Solar Panels in Shaded Areas
Shading can greatly reduce the efficiency of your solar panels. Since all the PV cells in a solar panel are wired together, a single shaded cell can lower the productivity of all others. If your solar panels are wired in string circuits, a single shaded panel can decrease the electricity output of the entire array.
Avoiding shadows during a solar panel installation can be challenging. Since the sun’s position in the sky is always changing, shadows constantly move. An area that seems ideal for solar panels in the morning may experience complete shade in the afternoon.
However, a professional solar installer can help you find the best placement for your solar system. Solar companies use simulation software to analyze shading conditions on your site throughout the year and can identify the ideal spot for solar panels.
Choose the Right Solar Panels
Even if you follow all the recommendations above, the rated efficiency of your solar panels is the main factor that determines overall system efficiency. Even if cleaned regularly, a 15% efficient panel cannot match the productivity of a 22% efficient panel. For this reason, it is important to talk with a solar installer to determine the right solar panel brand and efficiency for your energy needs.
What Are The Most Efficient Types of Solar Panels?
As we’ve discussed, monocrystalline panels generally have the highest efficiency. Comparatively, polycrystalline panels have an intermediate efficiency and thin-film solar panels tend to be the least efficient. But thanks to recent advancements in photovoltaic technology, some thin-film cells can now match the efficiency of crystalline silicon panels.
If you’re looking for specific product recommendations, the following manufacturers produce some of the most efficient solar panels in the industry.
Solar Panel Manufacturer | PV Module Efficiency |
Sun Power | Up to 22.8% |
Canadian Solar | Up to 22.8% |
REC | Up to 22.3% |
Panasonic | Up to 22.3% |
As of 2023, there are no commercial solar panels with a rated efficiency above 23%. However, solar cell technology is constantly evolving and this could change soon. Some PV cells have achieved an efficiency of nearly 50% in research facility conditions.
Factors That Impact Solar Panel Efficiency
Several factors can reduce the efficiency of your solar panels. Some factors (like weather) are unavoidable, but you can control others, like debris accumulation. High temperatures can negatively impact the productivity of your solar panels. There is nothing you can do about the weather, but you can look for solar panels with a low-temperature coefficient to mitigate the effect of heat. You can find panels with a coefficient below 0.30% per °C, which means they lose less than 3% productivity with a temperature rise of 10°C (18°F).
Dust accumulation and shading are also detrimental to solar panel efficiency, but unlike temperature, there is more room for control. Regular cleaning can help keep your solar panels operating at full potential, and you can avoid shading by using a professional installer to ensure adequate system placement. For example:
- If you have trees on your property, trim any branches that start growing on top of your panels. Also, watch for any leaves that gather on the surface of your panels.
- If you want to install an air conditioner or other rooftop equipment, choose a spot that will not cast a shadow on your solar array.
- New constructions can also cast shadows on your solar panels. Many states have solar easement laws prohibiting construction blocking your access to sunlight.
Conclusion:
Efficiency measures the ability of a solar panel to convert sunlight into usable, clean vitality. High-efficiency solar panels generate more electricity per square foot compared to standard panels. This is an advantage for homeowners with limited roof space, as you can use fewer high-efficiency panels to generate the energy you need.
However, high-efficiency panels tend to cost more, and paying the extra price only makes sense if you properly install and maintain your system. Dust accumulation and shadows can negatively impact energy production, even if you have the most effective Solar Panels in the market.
FAQ's
The most efficient solar panels range from 19% to 22.8%. This includes SunPower’s Maxeon panels, which are some of the most efficient on the market. Most solar panels have an efficiency rating of 15% to 20%.
Yes, but efficiency decreases very slowly. High-quality solar panels have an annual productivity loss that is typically less than 0.5%. Some solar manufacturers have achieved a degradation rate as low as 0.25% per year. However, the best solar panel manufacturers offer 25-year warranties, which cover repairs if you have issues with your panels over time.
Keeping your solar panels free of debris can help maintain efficiency. Solar companies recommend you clean your solar panels at least twice a year. Dust and other particles reduce the amount of sunlight your panels absorb, which can negatively impact their efficiency. It is also important to install solar panels in unshaded areas. Even a small shadow can reduce the energy output if it covers one PV cell completely.
No, most commercially available solar panels are less than 23% efficient. The National Renewable Energy Laboratory (NREL) achieved a solar cell efficiency of nearly 50% in 2020, but it used specific solar cells and a concentrated light source under highly controlled laboratory conditions.
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