First Solar vs SunPower: Who Makes Better Panels for Solar Farms?

First Solar (NASDAQ: FSLR) has been the undisputed solar manufacturing winner of 2017, booking at least 6.7 GW of solar panel sales and announcing a massive expansion that will bring up to 5.7 GW of capacity by the end of 2020. The threat of solar tariffs was a huge tailwind in both signings and the capacity expansion, but the new Series 6 product has helped as well.

Lagging behind has been SunPower (NASDAQ: SPWR), which is the solar industry's efficiency leader but has faced high costs that have shut it out of some markets. Utility-scale solar, where it competes head to head with First Solar, has been especially disappointing, and the company has lost sales because of the threat of tariffs.

Heading into 2018, both First Solar and SunPower are launching new products that could redefine their futures. For First Solar, Series 6 will start limited production in mid-2018, while SunPower's low-cost P-Series panels have made a big leap forward. Here's what you need to know about these key products in 2018.

First Solar's Series 6

The Series 6 solar panel that First Solar is so excited about is a panel that's about three times the size of the previous Series 4 panel and slightly more efficient. According to the latest data sheets, the highest efficiency panel is 1.232 meters by 2.009 meters and has a nominal power output of 445 watts, or 18% efficiency.

Panels aren't all the same, so efficiency goes all the way down to 420 watts and 17% efficiency, but for now the high end is what we'll use for this comparison because efficiency is always trending higher.

SunPower's P-19 solar panel

The competing P-Series product from SunPower is a mono-crystalline solar cell that's cut and shingled to create a product that's higher efficiency than those of competitors. The company has been making a multi-crystalline based panel called P-17 since 2015, but recently released the P-19 product.

According to the data sheet, panels are 2.067 meters by 0.998 meters and range from 385 watts to 405 watts, or 18.7% efficiency to 19.6% efficiency.

How First Solar and SunPower stack up

You can see above that First Solar's panels are slightly larger, which gives them higher wattage despite lower efficiency. In the table below I've outlined watts per square meter.

Efficiency isn't the only measure of output, but it's the most important. First Solar's thin-film panels perform slightly better at higher temperatures, which will increase output in some locations. Developers have detailed models to determine what output will look like with different solar panels, but efficiency is a good guide.

The other difference between First Solar and SunPower is that First Solar works with third-party racking companies. SunPower will sell panels on their own, but has also designed the Oasis power block, which contains racking, inverters, and even cleaning solutions for the P-Series product. Depending on the developer, either solution could be attractive.

Whose solar farm solution is better?

Based on bookings in the last twelve months, it seems like First Solar has momentum on its side. But the company is also nearly sold out of production for the next two years.

SunPower's product is newer on the market but is higher efficiency and is selling with a complete utility solution. What might change the narrative is the higher efficiency of P-19 solar panels. I'll also note that SunPower says it will soon be making a mono-PERC based P-Series solar panel that will be more efficient than the current P-19.

I don't know if there's a clear winner here unless we see SunPower gain some sales momentum. What I think is clear is that SunPower now has a product that's competitive, and may be superior to First Solar for solar farms, depending on the location. If that translates to higher utility scale sales in 2018 it'll be a huge win for SunPower, which is a big underdog to the bigger First Solar right now.

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Travis Hoium owns shares of First Solar and SunPower. The Motley Fool recommends First Solar. The Motley Fool has a disclosure policy.