When you’re shopping for solar panels, one of the things that manufacturers usually tout is efficiency. A high efficiency panel turns more sunlight into electricity than a lower efficiency panel, which means a solar homeowner can get more out of their limited rooftop space.
So if efficiency is a good thing, that must mean that you should shop for the highest efficiency panels you can get, right?
No, not always. If you’re in a situation where it’s important to maximize your power generation - like if you have a small roof - then efficiency could be very important to you. With a higher efficiency panel, you need less space to generate the same amount of electricity.
If you’re looking for the highest efficiency, you’ll be shopping for monocrystalline solar panels.
Monocrystalline and polycrystalline solar panels are the two types of silicon solar panels that you will find on the market. They differ in their manufacturing process, and produce solar cells with different characteristics.
Silicon for monocrystalline solar cells is cut from an ingot of silicon that is a single, unbroken crystal. This requires a very high purity silicon and is more difficult to manufacture than polycrystalline. Mono cells are more efficient, less affected by high temperatures, and perform better in low light compared to poly cells. They also have an even black color that many people prefer.
Polycrystalline silicon cells are cut from a block of silicon made of smaller grains of silicon, giving a poly solar cell a flakey appearance due to the grain boundaries, as well as a blue tinge. Compared to monocrystalline silicon, poly generally performs a little worse and is less efficient. The main benefit of poly cells is that they are less expensive due to less complex manufacturing.
While monocrystalline is tops when it comes to efficiency, it’s also generally more expensive. Polycrystalline, while less efficient, is often cheaper, sometimes significantly. That means that if you’re trying to balance price and efficiency, it’s often a better deal to look for higher efficiency polycrystalline panels.
Not all of the efficiency differences in solar panels are due to silicon. Improvements in wiring and innovations like half-cut cells have allowed polycrystalline cells to improve and keep pace with monocrystalline panels.
As you’ll see in the tables later in this article, the performance difference between the best monocrystalline and polycrystalline panels isn’t that great. The top polycrystalline panels currently have an STC efficiency of 18.5%, which isn’t very far from the performance of the top performing monocrystalline panels that reach 22.7% STC efficiency.
That relatively small difference in efficiency can come at a cost. A monocrystalline panel from a premium manufacturer like SunPower might cost twice as much as a polycrystalline panel that is only a few percent less efficient.
While premium manufacturers like LG and SunPower offer some of the best warranties on the market (such as 25 year product warranties), that advantage is shrinking as well, with REC Solar offering a 20 year product warranty on all its panels, including its less expensive polycrystalline lineup.
Pricing isn’t listed here because it can fluctuate significantly, and also depends on what your solar installer is able to negotiate with its suppliers. However, there are a few companies that try to capture the high end of the market, including SunPower and LG. You can expect to pay more for these compared to manufacturers like REC Solar and Hanwha Q CELLS, which also produce quality products but at a lower price point.
In the tables below, you’ll notice that Watts and Efficiency for the panels are listed in both STC and PTC ratings.
STC refers to Standard Test Conditions, and is the performance of the panel at a solar cell temperature of 25°C and light intensity of 1,000 W/m² (watts per square meter). The STC wattage is the number you’ll see advertised for the panel.
PTC is the PVUSA Test Calculation, and differs from STC in how the solar panel is tested. Instead of measuring the temperture of the cell, the PTC test specifies an air temperature of 20°C. This is important because a dark solar panel sitting in the sun will get a lot warmer than the surrounding air. Solar cells lose efficiency when they’re hot, so the PTC test results in a hotter cell than the STC test. It also specifies a lower light intensity of 800 W/m².
What do these mean for the consumer? The STC rating represents how a solar panel might perform in perfect conditions, but the PTC rating will give you a more accurate idea of how it will perform in the real world.
Both measurements are useful to have, especially because solar panels differ in their ability to perform well in the heat. As a consumer, we recommend that prioritize the PTC rating when comparing different panels.
These are the highest efficiency monocrystalline solar panels available in 2019 for the residential market. If you come across a panel with a higher wattage, check if they are a larger panel intended for commercial or utility use. These panels will be longer than one intended for home use.
|Company||Model||Watts (STC)||Watts (PTC)||Efficiency (STC)||Efficiency (PTC)|
|Silfab Solar Inc.||SLA320BC||320||300.6||21.92%||20.59%|
|REC Solar||REC365AA Black||365||345.2||21.60%||20.43%|
|REC Solar||REC360AA Black||360||340.3||21.30%||20.14%|
These are the highest efficiency polycrystalline solar panels available in 2019 for the residential market.
|Company||Model||Watts (STC)||Watts (PTC)||Efficiency (STC)||Efficiency (PTC)|
|REC Solar||REC290TP IQ||290||268.9||18.27%||16.94%|
|REC Solar||REC290TP IQ BLK||290||268.9||18.27%||16.94%|
|REC Solar||REC290TP Q2||290||268.9||18.27%||16.94%|
|REC Solar||REC290TP Q3||290||268.9||18.27%||16.94%|
|Canadian Solar Inc.||CS6K-285P||285||264.4||18.04%||16.73%|
|Hanwha Q CELLS||Q.PEAK G3.1 305||305||279.2||18.26%||16.72%|
|Hanwha Q CELLS||Q.PEAK G4.1/SC 305||305||279.2||18.26%||16.72%|
|Hyundai Energy Solutions||HiS-M305TI||305||273.3||18.63%||16.70%|
|Hanwha Q CELLS||Q.PLUS-G3 280||280||255.5||18.25%||16.66%|
|REC Solar||REC285TP IQ||285||264.1||17.96%||16.64%|
|REC Solar||REC285TP IQ BLK||285||264.1||17.96%||16.64%|
|REC Solar||REC285TP Q2||285||264.1||17.96%||16.64%|
|REC Solar||REC285TP Q3||285||264.1||17.96%||16.64%|
|REC Solar||REC300TP2 Q2||300||277.2||17.96%||16.60%|
|REC Solar||REC300TP2 Q3||300||277.2||17.96%||16.60%|
|REC Solar||REC290TP2 BLK||290||267.9||17.90%||16.54%|
|Hanwha Q CELLS||Q.PEAK G3.1 300||300||274.5||17.96%||16.44%|
|Hanwha Q CELLS||Q.PEAK G4.1/SC 300||300||274.5||17.96%||16.44%|
|Hyundai Energy Solutions||HiS-M300TI||300||268.6||18.33%||16.41%|
|Hanwha Q CELLS||Q.PLUS-G3 275||275||250.8||17.93%||16.35%|
|REC Solar||REC280TP IQ||280||259.4||17.64%||16.35%|
|REC Solar||REC280TP IQ BLK||280||259.4||17.64%||16.35%|
If you’re a homeowner planning to install solar panels, what’s the best choice for you?
The first thing to determine is if the footprint of the array is paramount. If you have a small roof that you want to fit as many panels as possible, or simply want to minimize the physical size of your array, go ahead and consider monocrystalline panels. Both LG and SunPower make great products, and both include industry-leading 25 year product and power warranties.
However, if you want to save some money and you’re willing to use slightly more space for your array, we recommend that you consider polycrystalline panels. You’ll give up a few percent in efficiency, but you could save a substantial amount of money.
The exact cost will depend on your installer. If there is a specific panel you’d like to consider, ask your installer to get you pricing.
With these considerations in mind, we think that the REC Solar TwinPeak 2 series is one of the best choices for the average homeowner. It has the highest efficiencies of any polycrystalline solar panel, and also comes with an excellent 20 year product warranty and 25 year power warranty.
In most cases, solar panels from REC Solar should cost a quite a bit less than premium solar panels that have only a few percent better efficiency.
And no, they didn’t pay us to say that! Looking at the numbers, the TwinPeak 2 simply makes a lot of sense.