Efficiency is a word we use about our cars, our homes and even our day-to-day work. But what does it mean in the world of solar panels?
Solar panel efficiency is a measure of how much of the sun’s energy a solar panel turns into usable electricity.
«If something is 20% efficient, that means that 20% of the energy in that sunlight reaching the solar panel gets turned into moving electrons,» Daniel Ciolkosz, professor of agricultural and biological engineering at Pennsylvania State University, told CNET.
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A more efficient solar panel will create more electricity than a less efficient one, even if they’re exposed to the same amount of sunlight.
The highest solar panel efficiency on the residential market today are sold by SunPower and Canadian Solar. Both have a maximum efficiency rate of 22.8%. But competitors are closing the gap.
Choosing the best solar panels for your home is a game of balancing price, function (like efficiency) and perhaps even aesthetics. Your choice is also limited by what your chosen solar installer actually offers.
This list ranks the most efficient solar panels. Not only will we tell you which panels get top marks for turning the most sunlight into energy, we’ll explain just what solar panel efficiency is, why it’s important and if it actually matters.
Most efficient solar panels
Determining the highest solar panel efficiency is a pretty simple matter of tracking down manufacturer-provided data sheets and locating the efficiency numbers. Those numbers today are higher than in the not-too-distant past and keep creeping upward.
According to the Lawrence Berkeley National Laboratory’s Tracking the Sun report, 2021 was the first year more than half the residential solar panels installed in the US had an efficiency ratings above 20%. Ten years ago only 0.6% of those installed reached that mark. High-efficiency solar panels are more common than ever and becoming only more so.
If you’re looking for the most efficient solar panel for your roof, here’s how the most widely used brands on the market stack up.
Data accurate as of April 2023.
How we chose and ranked the most efficient solar panels
The panels on this list were chosen because they’re some of the most commonly installed panels and are likely to appear on quotes for solar installations. If you’re quoted for panels that don’t appear on this list, you can check their efficiency rating and other specifications in the same way I did. Here’s how.
Solar panel manufacturers publish data sheets for solar panels, which detail their dimensions, performance metrics and internal chemistry. If your solar company doesn’t provide you with them, you can access them by clicking on the company name in the table above. (Many of the links lead to PDFs.) From there, it’s a simple matter of comparing statistics.
The panels featured here are the most efficient offering from each of these companies. They may sell other panels that would appear higher on the list. In general, the higher a company appears on this list, the more efficient all of the solar panels they offer are.
What affects solar panel efficiency?
The numbers listed above are obtained under controlled conditions in laboratory tests. In the real world there are plenty of factors that might cause you to receive less energy than a panel’s efficiency rating would suggest. Hazy skies, suboptimal angle or placement on your roof or inefficient electronics between your panels and the things they’re powering all could result in a lower actual power output.
Another factor affecting solar panels efficiency is their temperature. As solar panels get hot, they start to produce less energy, though not at the same rate. A solar panel’s temperature coefficient measures how much worse its production gets for every degree Celsius (1.8 degrees Fahrenheit) it gets above 25C (77F).
For example, at 26C (79F) a REC Alpha Pure would produce 0.24% less energy than at 25 degrees. At 29C (84F), it would lose just shy of 1% of its production.
Is solar panel efficiency important?
All things being equal, it would make sense to choose a higher-efficiency solar panel over one with a lower rating. But high-efficiency solar panels typically cost more than lower rated ones, so making the best choice becomes a matter of balancing your financial goals with what your preferred installer offers and other considerations like brand and aesthetics.
«It’s just one part of the equation,» said Ciolkosz. «The bigger question for the end user is the economics and how it’s paying off.»
Is there a case where efficiency might be a worthwhile consideration?
«If you have one of those tiny homes on HGTV,» said Tom Beresnyak, a Pennsylvania State University extension educator.
If you’re limited by available space for solar panels, you might want to squeeze out as much solar energy as possible from that space, though if your state allows it, a community solar subscription still might be a better choice financially, Beresnyak said.
What should I consider when choosing a solar panel company?
Because there’s no one-size-fits-all solar solution, there’s no one-size-fits-all advice for choosing a solar company. The best approach is to get quotes from multiple installers before deciding. Choose the company that has offered you the best fit for your needs, you trust to do the work and has answered all your questions.
You should understand your energy usage before going solar and decide whether your goals are to completely replace that energy, save as much money as possible or achieve something else. From there, it’s a matter of measuring competing quotes against your goals.
The Department of Energy recommends that you choose an installer with credentials from a respected third party, like the North American Board of Certified Energy Practitioners, which operates an online directory of certified installers that you can filter by state and certification.
Installers should definitely assess your roof condition because removing panels at a later date to replace a roof will be an additional cost. They should also be able to transparently answer questions about the systems design and why they’re making their specific proposal.
«The installer can make a huge difference because the angle and the mount [are important for] maximizing what you have at that location — a skilled installer is still going to be the real key in your long term production,» Beresnyak said.