Tesla 400 and 425 watt solar panels: an overview
After years of installing solar panels from other manufacturers and the end of a partnership with Panasonic, Tesla is now using its own brand of solar panel.
Tesla’s Energy division gets less attention than its vehicles, but it continues to plug along, with 345 MW of solar panels installed in 2021.
For many years, Telsa (and SolarCity before it was acquired by Tesla) installed solar panels from other manufacturers, including Q Cells, LG, and Panasonic. For a few years, Tesla and Panasonic had a partnership to manufacture solar panels at the Gigafactory in Buffalo, but that relationship ended in 2020.
While the Buffalo Gigafactory apparently continues to manfacture the Tesla Solar Roof, it doesn’t appear that solar panel manufacturing is happening there anymore.
Even so, you can still buy a solar installation from Telsa, and that will come with Tesla-branded solar panels. Tesla publishes little information about its solar panels, so it’s not clear where they are currently being manufactured. That said, some basic specifications are available. At the moment, Telsa appears to be installing 425 watt and 400 watt panels.
Current Tesla solar panels: 425 watt and 400 watt models
Tesla seems to be installing two models these days: the Tesla T400H and the T425S. The T400H is a 400 watt panel with an efficiency of about 20.4%, and the T425S is a 425 watt panel with an efficiency around 19.6%.
If you’re wondering why the 425 watt panel has a lower efficiency but higher output, it’s because it’s a physically larger panel. This can simplify the installation process because the crew has fewer panels to deal with, but the larger panel might not fit on all rooftops. Here’s a list of the basic specifications:
|Tesla T425S||425 watts||19.6%||82.4" x 40.9"|
|Tesla T400H||400 watts||20.4%||74.4" x 41.2"|
Not much else is stated about this panel, except that it uses half-cut cells that improve efficiency in shaded conditions and is available only in an all-black design.
Tesla T425S: full specifications
|Power output (STC)||425 watts|
|Power output (NMOT)||317.4 watts|
|Temperature Coefficient (PMax)||-0.331%/1°C|
|Open Circuit Voltage||48.65 V|
|Short Circuit Current||11.24 V|
|Max Power Voltage||41.05 V|
|Max Power Current||10.36 V|
|Front side load (snow)||3600 Pa|
|Back side load (wind)||1600 Pa|
|Power Warranty||85% after 25 years|
|Product Warranty||25 years|
Tesla T400H: full specifications
|Power output (STC)||400 watts|
|Power output (NMOT)||300.1 watts|
|Temperature Coefficient (PMax)||-0.34%/1°C|
|Open Circuit Voltage||45.3 V|
|Short Circuit Current||11.14 V|
|Max Power Voltage||37.13 V|
|Max Power Current||10.77 V|
|Front side load (snow)||3600 Pa|
|Back side load (wind)||2660 Pa|
|Power Warranty||86% after 25 years|
|Product Warranty||25 years|
How do Tesla’s panels compare?
With an efficiency rating of around 20%, Tesla’s solar panels are good, but fall short of the most efficient panels on the market. Tesla’s panels are on par with panels from leading Chinese brands such as Jinko and Trina Solar.
Here’s a table comparing the 400 watt and 425 watt Tesla panels to models from some popular manufacturers. Remember that power output, while a useful metric, can be misleading because not all panels are the same size. That’s why efficiency is the first number listed here.
|Tesla T425S||19.6%||425 watts||25 years|
|Tesla T400H||20.4%||400 watts||25 years|
|Trina Solar Vertex S||21.1%||405 watts||12 years|
|Jinko Solar Eagle G4||20.96%||400 watts||12 years|
|REC Alpha Pure||22.2%||410 watts||25 years|
|SunPower M-Series||22.0%||425 watts||25 years|
|Q.Peak DUO-G10||21.5%||380 watts||25 years|
|Solaria PowerXT 370R-PD||20.5%||370 watts||30 years|
As you can see, Tesla’s panels stack up well when it comes to efficiency and warranty, but fall short of the best performers such as REC and SunPower, which both offer higher efficiency and a better warranty that includes labor costs.
In addition, Tesla’s temperature power coefficient - a measure of how the panel’s power output is negatively impacted by high temperatures - is also worse than panels offered by REC and SunPower, which respectively lose 0.26% and 0.29% in efficiency for every 1°C increase in temperature, which is less than Tesla’s loss of 0.34%. This might seem like a small difference, but it may become noticeable on the hottest days of the year.
Weaker strength ratings?
One curious thing about Tesla’s panels is that they have the weakest strength ratings of any panel I’ve seen. According to Tesla’s datasheet, their panels have a front side rating of 3,600 Pa and a back side rating of 1,600 Pa for the 425 watt model and 2,660 for the 400 watt.
Pa is Pascals, and measures how much pressure the panel can withstand from the front or back of the panel before breaking. The front side rating is sometimes called the snow load, and the back side is sometimes known as wind load. This is because roof mounted panels might be buried underneath a few feet of snow in some climates, and ground-mounted panels might have to deal with gale-force winds from the rear.
The lowest strength ratings I’ve seen on any panel sold for residential use are 5,400 Pa front side and 2,400 Pa back side. Many panels are even stronger: for instance, the REC Alpha Pure mentioned above has a rating of 7,000 Pa and 4,000 Pa.
Tesla claims their panel passes the standard hailstone test of 1-inch hail at 51 mph, so it’s not clear what these lower strength ratings might mean for the average consumer who doesn’t have extreme weather to contend with.
Should you choose a Tesla panel?
Tesla’s panels perform well: they have good efficiency and come with a 25 year product warranty. While there are limitations when choosing a Tesla solar system - notably, limited choices when it comes to system size and some poor company reviews - the panels themselves aren’t a bad choice, especially if the price is right.
However, if you live in a snowy climate or an area where wind storms are a concern, you might have second thoughts about these Tesla panels due to their oddly low strength ratings.
By the way, if you’re interested in the Tesla Solar Roof - a completely different product that is a roof replacement using solar panels that mimic conventional roofing tiles - you’ll want to check out our article on solar shingles.