SunPower solar panels: the unofficial product guide

Among the premium solar panel manufacturers that are popular in the US, California-based SunPower stands out. Their solar panels are at the top end of efficiency, but they also have an extensive dealer network to support a 25 year product warranty.

The strong warranty and installer certification program are some of the reasons why The Solar Nerd network includes several SunPower dealers. While this might make it seem like we’re biased toward SunPower, there are other excellent brands worthy of consideration, such as LG and Solaria.

To make an informed decision between SunPower and other solar panel brands, you’ll want to take a close look at their product lineup. Unfortunately, SunPower doesn’t make it very easy for the consumer to understand the differences between their product series, which are simply named with single letters such as X-Series and E-Series.

Is X better than E, or is it the other way around? This guide will help you decipher SunPower’s products, and choose the best one for your particular situation.

SunPower A-Series: Best choice if you want maximum performance or have some shade on your roof

If you’re working with limited roof space, or simply want to generate the maximum amount of electricity with the smallest footprint on your roof, the SunPower A-Series is going to be your best choice.

You might also choose the A-Series if you have a roof that is impacted by shade for part of the day. (If your roof is mostly or fully covered by shade, solar panels are probably not for you!) This is because the A-Series is what’s known as an AC solar panel. This means that it is a conventional solar panel that is integrated at the factory with a microinverter.

An inverter converts DC electricity generated by a solar panel to AC electricity that your home can use. Every home solar system has at least one, but more advanced microinverters pair an inverter with each solar panel in the array. This improves expandability, allows a microinverter-based system to handle shading better, and may reduce installation costs. You can read our article on AC solar panels to learn more about these.

SunPower Gen 5 cells

The A-Series uses SunPower’s newest Gen 5 Maxeon solar cells. These cells are 65% larger than the previous Gen 3 cells. The residential A-Series panels have 66 cells, while the X-Series panels with the older Gen 3 cells use 96 cells. This means less space is wasted by the spacing between cells with the larger Gen 5.

Highest efficiency SunPower panels

With the latest generation solar cells, the A-Series panels range from 390 watts and 20.9% efficiency up to 425 watts and 22.8% efficiency. (There are also larger panels intended for commercial applications that hit 450 watts.)

One thing to note when comparing the wattage of the A-Series - 425 watts at the top end - to other panels is that the A-Series is slightly larger. The A-Series is 40" x 72" (2,880 square inches), which is larger than the 41" x 61" (2,525 square inches) X-Series and E-Series. So, to make a fair comparision, refer to the efficiency rather than wattage.

The power temperature coefficient for the A-Series is –0.29%/°C, which means that the panel loses 0.29% efficiency for every 1°C increase in temperature. This is an excellent rating, and outperforms most other panels you’ll find on the market.

SunPower X-Series: High efficiency without built-in microinverters

If you want very high efficiency solar panels but without built-in microinverters, your best choice is SunPower’s X-Series.

The X-Series is known as a DC panel because it’s a conventional panel that generates DC electricity and isn’t paired at the factory with a microinverter. You can still use microinverters with this panel if you want, so you might choose the X-Series if you want SunPower panels but prefer a different microinverter, such as the Enphase IQ series.

The X-Series uses SunPower’s Gen 3 cells. They are a smaller and older cell than the latest Gen 5, but are still very efficient, reaching a maximum of 22.7%.

The panels in the X-Series range from 327 watts and 20.1% efficiency, and reach as high as 370 watts and 22.7% efficiency.

Just like the A-Series, the X-Series panel has an excellent power cofficient rating of –0.29%/°C.

If you live in a location where your panels will be subject to severe stresses such as hurricanes or heavy snow loads, you’ll want to be aware that the X-Series has a Gen 3 and a Gen 5 aluminium frame.

With the Gen 3 frame, the X-Series panels are rated for 2400 Pa wind (rear) load and 5400 Pa snow (front) load. The Gen 5 is a little stronger: 3000 Pa wind (rear) load and 6000 Pa front (snow) load.

If severe weather isn’t a concern, either Gen 3 or 5 versions will be fine for you.

A final thing to keep in mind (as mentioned above already) is that the X-Series is slightly smaller than the A-Series. This means, in a roof layout, the two panels won’t fit in exactly the same space.

All-black solar panels

The X-Series also includes the Signature Black panels, which are all-black panels that can be a nice choice if curb appeal is important to you. All-black solar panels are often a better, cheaper alternative to solar shingles when aesthetics are important.

SunPower E-Series: Best lower cost choice

The E-Series is a lower cost choice from SunPower, but is still a very high performance panel that hits 20.4% efficiency, making it more efficient than the highest efficiency panel from other manufacturers. It uses SunPower’s older Gen 2 series solar cells, with each panel containing 96 cells.

There are only two panels in the E-Series: a 320 watt panel rated at 19.9% efficiency, and a 327 watt panel with 20.4 efficiency.

The power coefficient is –0.35%/1°C, which is slightly worse than the A-Series and X-Series. This means that E-Series will lose more power in hot weather than the X or A panels.

Just like with the X-Series, the E-Series comes with two frames: the Gen 3 and a stiffer Gen 5. The physical dimensions of the E-Series is the same as the X-Series (41" x 61").

SunPower P-Series: solar panels for commercial applications

The SunPower P-Series is a larger solar panel designed for commercial applications, such as solar farms.

If you’re wondering what’s the difference between a commercial solar panel and one that is intended for homes, it’s because of OSHA (Occupational Safety and Health Administration) rules that limit the weight that a rooftop installer can carry to 50 pounds. If a panel is larger than 50 pounds, two installers are required to carry it, adding to the cost of installation.

Commercial solar panels are also larger: 81" long in the case of the P-Series, compared to 61" with the X- and E-Series.

What is SunPower Equinox?

If you look at the SunPower website, you’ll see the Equinox brand mentioned prominently. Equinox isn’t a particular solar panel product, but rather their name for a packaged solar system that includes SunPower racking and even a battery system. It’s a soup-to-nuts package of SunPower equipment, under one brand name.

When you choose a SunPower Equinox solar system, you’re getting the A-Series solar panels, the SunPower InvisiMount racking system, and the EnergyLink monitoring system that connects to the A-Series inverters.

You can add the SunPower SunVault battery storage to the Equinox system too.

What is Maxeon?

SunPower used to manufacture its own solar cells. But solar panel manufacturing is a highly competitive buisness, and after years of bleeding money, SunPower split off the manufacturing side of its business into a new, independent company called Maxeon. The new company is based in Southeast Asia, and SunPower continues to use Maxeon cells in its products. SunPower is the exclusive seller of Maxeon cells in North America, so there are no other companies that use Maxeon cells in rooftop solar panels (you can find Maxeon cells in some flexible solar panels intended for RVs and other portable applications.)

Alternatives to SunPower

One of the great things about SunPower, and the reason that The Solar Nerd network includes many SunPower installers, is the great dealer network and extensive warranty. Their certified dealers carry ratings, from standard certified companies to Master dealers, which is a designation reserved for the very best companies in their network. If you request quotes for a solar installation and a SunPower Master dealer is available in your area, we’ll usually include it in the companies we refer to you.

But SunPower isn’t the only premium solar company with a great warranty and certified dealer network. Panasonic and LG are excellent brands in this category, and there are other brands with high efficiency and 25 year warranties. Check out our article on solar panels with great warranties to learn more.