Are you a meticulous number cruncher who breaks out the spreadsheet whenever you’re planning a big product purchase?
If you are, you might conclude after running the numbers that the all-in cost of a system based on budget solar panels is better than one based on premium panels. After all, high-end solar panels can cost roughly 50% more than budget panels, and the increase in electricity generation you get from premium panels might never pay back that initial difference in price.
While at first it might seem obvious that a cheaper solar panel will save you money versus a more expensive panel, it’s actually not always true. While the sticker price of a lower efficiency panel may be less, over the long run you can often save money by going with a better panel.
This is because high efficiency panels require less space to generate the same amount of power, which means that you need less racking hardware, which also means lower labor costs because there’s less equipment to install. A smaller footprint on your roof also means fewer holes to drill and a lower chance of leaks.
The best panels on the market also come with 25 product year warranties, which covers the cost of a replacement - and sometimes the labor cost of the replacement - in the unlikely event of a failure. Cheaper panels often come with only 10 year product warranties that don’t include labor, which means you’ll pay the cost of the de-installation and re-installation of the replacement panel, which might totally eat up the savings you got from choosing a cheaper panel.
Plus, it’s often comforting to know that you have the best product available. This is especially the case when it comes to solar panels which, in the ideal case, you install and then simply forget about for 25 years or more. That kind of peace of mind may easily be worth a higher upfront cost.
So which are the best solar panels for your home? That depends on what matters most to you, so this article will look at four different factors: warranty, reliability, thermal performance, and overall efficiency.
Right off the bat, we’ll mention two things that I’ve written separate articles about recently: warranty and reliability.
A really good solar panel warranty will cover not only product failures for 25 years, but also the labor cost of removing the failed panel and installing a new one. This is valuable because the cost of paying someone to climb onto your roof to replace a failed panel can easily exceed the cost of the panel itself.
Cheaper panels come with only a 10 year product warranty with no labor coverage, which means that a more expensive panel with a better warranty could actually save you money in the long run if you experience a failure.
This raises the question: how likely is it for a panel to fail? Fortunately, solar panels are generally extremely reliable - but that doesn’t mean that they are all equally reliable.
Accelerated testing by independent labs, where they put solar panels in an environmental chamber and subject them to all kinds of abuse, is one way to predict if the panel you buy today really will last for 25 years. You can read our article on solar panel reliability to learn about the accelerated testing results performed by the PVEL lab.
According to the 2020 PVEL reliability scorecard, here are the top 5 most reliable solar panel brands:
These five solar panel manufacturers provide the best warranties in 2020:
Again, to learn more, read my article about the best solar panel warranties.
Solar cells lose efficiency as the temperature increases. The best operating condition for a solar panel is a cold sunny day, but much of the time your solar panels will be getting baked in the hot sun.
This why it’s important to pay attention to the temperature coefficient of a solar panel, especially if you live in a hot climate.
You can read my article on making sense of solar panel specifications if you want to learn a lot more about interpreting the cryptic you’ll find on a solar panel datasheet, but the number to pay attention to for thermal performance is the power temperature coefficient, which is often listed as “temperature coefficient (Pmax)”.
The power temperature coefficient tells you how much the efficiency of a solar panel drops as the temperature of the panel increases. It is shown as a percentage drop in efficiency for every 1 degree Celsius increase (about 1.8°F) in temperature.
For example, the SunPower X-Series panels have a power temperature coefficient of -0.29%/°C. This means that it loses 0.29% efficiency for every 1°C increase in temperature.
How does that compare to a cheaper panel? A lower cost Renesola panel that I found has a power temperature coeffient of -0.40%/°C, or about 38% worse than the X-Series SunPower panel. This means that even if two panels have a similar wattage, the one with a better temperature coefficient will perform better in the real world.
The solar panels below are the top five for temperature coefficient, which means they would be good choices for operating in high temperature environments.
|Manufacturer||Panel||Temperature Coefficient (% per °C)|
|First Solar||Series 6||-0.32%|
Higher numbers (ie. closer to zero) are better, so the Panasonic HIT+ Series is the best in this group, followed very closely by the REC Alpha series.
The First Solar Series 6 is notable because it uses thin-film technology versus the crystalline silicon (c-Si) technology that used in nearly every other panel on the market. Thin-film technology is eclipsed in manufacturing volume by c-Si panels but it theoretically has some advantages, such as better low-light performance.
The overall efficiency of a solar panel refers to how much of the incoming sunlight gets converted into electricity. Higher numbers are better, and over the past decade the efficiency of solar panels aimed at the residential market has increased from the mid-teens to above 20%. This reflects the introduction of several improvements in technology, such as heterojunction cells, PERC cells, and half-cut cells.
Here are the five solar panels with the best nameplate efficiency:
I mention nameplate efficiency because, as discussed above, the real-world efficiency of a solar panel is affected by temperature, so even if a solar panel has really high efficiency under lab conditions, it might not maintain that high efficiency in the real world.
This is why it’s important to look at both the efficiency and thermal coefficient when researching a solar panel.
For example, at first glance it looks like the Jinko Solar Tiger, with an efficiency of 20.96%, is higher performing than the Panasonic HIT+ series, which is 20.2% efficient. However, the Panasonic panel has a much better thermal coefficient: -0.258% vs -0.35% with the Jinko panel. This means that the Panasonic panel would probably perform better on top of your hot roof, even though it’s listed as having a lower efficiency.
One other thing to mention: these are product lines, and most manufacturers have panels with multiple wattages within a series. For example, the Jinko Tiger series includes panels ranging in output from 345 to 365 watts.
The meaning of “best” is different for everyone, so understand what’s important to you before choosing a panel. Do you really want the peace of mind of never having to deal with a system failure? Look for a panel that’s done well in independent reliability testing and has a great warranty.
Or maybe you really want to squeeze the maximum amount of electricity out of your limited rooftop space? Then go for a panel with high efficiency - but remember that thermal performance will be an important factor too.
Still can’t decide? Go with price. The difference between a 22.2% and a 21.7% efficient panel is really small, so if there’s a difference of a couple thousand or even a few hundred dollars in price, any gain in power production from that minor difference in efficiency will probably never make up that differential in sticker price.