400-watt panels: Why to get them, and which ones are best in 2021

Updated

Two sleek black 400 watt solar panels 
400-watt solar panels are being used in a rising share of residential solar installations. Image source: LG Solar

Solar panels are getting bigger. Just five years ago, the biggest solar panels were barely 300 watts. Now, in 2021, we’re seeing the release of residential solar panels measuring in at 400 watts, or even larger.

The increase in solar panel size has been made possible by advancements in solar cell technology. But the proliferation of new solar panels that are 400 watts-plus also has to do with one-upmanship between solar panel manufacturers, with each eager to prove that their solar panel is the biggest.  

But when it comes to solar panels, does size really matter? Is a solar panel 400 watts (400 W) in size a better choice for your home than a more common 300-350 W panel? And which of the 400 W solar panels currently on the market are worth considering? We’ll answer these questions in this blog. 

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    What is a 400-watt solar panel?

    Solar panels are sized based on their output capacity. A 400-watt solar panel is a solar panel capable of producing 400 watts of instantaneous DC electricity under ideal Standard Test Conditions (STC). 

    What is the daily power output of a 400-watt solar panel? 

    In real-world conditions, a 400-watt solar panel will produce, on average, between 1,200 watt-hours (1.2 kilowatts-hours, or 1.2 kWh) and 3,000 watt-hours (3 kWh) of DC electricity per day, depending on your location. 

    You can check the exact figure for where you live using the peak sun hours figure for your location. Sunny locations in Texas, for instance, get 6 peak sun hours (PSH) per day, on average. Simply multiply panel wattage by the number of PSH  - 400 W x 6 PSH - and we see average daily power production would be 2,400 watt-hours (2.4 kWh) there. 

    Can I use 400-watt solar panels for my home? 

    Yes. You can wire together several individual 400-watt panels to build the solar system size you need

    A typical 6 kW home solar system, for instance, would be built by installing fifteen (15) 400-watt solar panels on the roof. Several major solar panel brands - including LG and SunPower - now offer 400-watt solar panels for home and commercial use. 

    However, as of 2021, 400-watt solar panels are still an uncommon size in residential solar power installations, with most consumers opting for panels in the 300-350 watt range. 

    Can I use 400-watt panels for my RV or boat? 

    Yes. RVs and boats have limited space and power requirements, so they could use a single 400-watt solar panel for their off-grid power needs. 

    However, it’s more common for RVs, boats, and similar setups to use 400-watt starter kits. They usually comprise four (4x) 12 volt 100 watt panels - which combine to make 400 watts of solar capacity - along with an MPPT inverter, solar charge controller, AGM battery bank, extension cables, and mounting hardware. 

    Four hundred (400) watt solar panel kits are available from companies like Renogy, Grape Solar, and Windy Nation through Amazon.  

    The best 400-watt solar panels

    Here are the best solar panel models that are 400 watts in size, or slightly bigger. 

    We’ve chosen solar panels made exclusively by the best solar panel manufacturers: all are among the top 10 brands with the highest consumer review scores.  

    All of the solar panels on this list are monocrystalline solar panels, aka mono solar panels. In 2021, monocrystalline is the preferred cell type for high-efficiency and high-wattage panels.  

    400-watt solar panels by the top solar brands
    Brand Panel model Wattage Efficiency
    Canadian Solar† HiKu Mono PERC series 400-425 W 19.7 - 20.9%
    LG† LG400N2W-A5 400 W 19.3%
    LG LG405N2W-A5 405 W 19.5%
    Mission Solar MSE SX6W 405 - 425 W 18.4 - 19.3%
    Mission Solar MSE SX6Z 415 - 425 W 18.9 - 19.3%
    Silfab Solar SIL-400 NU 400 W 19.6%
    SunPower† A Series Residential 390-420 W 20.9 - 22.5%
    SunPower SPR-E19-410-COM 410 W 19.1%
    SunPower SPR-E20-435-COM 435 W 20.3%
    Trina Solar† Tallmax TSM-DE15M(II) 390 - 415 W 19.2 - 20.4%

    †Also a SolarReviews experts’ choice brand  

    For this list, we’ve only included solar panels that have cell configurations suitable for home use, i.e. 60-cell (120 half-cell), 72-cell (144 half-cell), or sizes that fall in between. 

    It’s worth noting that there are solar panels that are even bigger; Trina Solar, for example, now offers a massive 120-cell, 600-watt solar panel. However, these solar panels have a very large physical footprint and are only really suitable for solar farms. 

    Are 400W solar panels expensive?

    Yes, 400 watts cost more than panels that are a smaller size. And 400-watt panels don’t cost more because they produce more power; they’re more expensive in relative terms as well, i.e. they cost more per watt. 

    Solar panel manufacturers have to employ more advanced manufacturing processes to produce a solar panel that produces more power without a corresponding increase in size. Further, 400-watt panels are new, higher-end models, and solar panel makers tend to include a higher margin on these products. 

    Expect to pay a premium of roughly 5-10% per watt if you build your solar energy system using 400 W solar modules over modules in the more standard 300-350 W range. 

    Reasons to get 400-watt solar panels

    There are two major reasons to get 400-watt solar panels as opposed to the more common 280 to 350-watt solar panels: when you have a small roof, and to ensure you have less points of failure in your panel.

    Make the best use of a small space 

    A lack of roof space is the biggest reason to get a 400 W (or bigger) solar panel

    The largest solar panels - those that are 400 watts or more in size - are built using the most efficient solar cell technologies. The more efficient a solar panel is, the less space it takes to produce a given amount of power. 

    So if you’re trying to squeeze the maximum solar power out of a given space, look for 400-watt solar panels with a module efficiency of 20% or higher. 

    Learn more: Most efficient solar panels in 2021

    Less points of failure 

    If you use 400-watt solar panels, you are less likely to have problems with your system over the life of the panels

    Why? Because using 400-watt solar panels cuts down on the number of modules used. A 6 kW solar system can be built with fifteen (15) 400-watt panels, as opposed to twenty (20) 300-watt panels. 

    While solar panels themselves are unlikely to fail, the chances of failure with allied equipment are higher. For instance, module-level power electronics (MLPE) - microinverters and power optimizers - are often used with each individual panel to meet code requirements.

    By using fewer panels, you reduce the need for MLPE, and thus there’s a much lower chance you’ll encounter problems both within and outside your warranty period. 

    Number of 400-watt panels and roof space required

    Most homeowners installing a solar energy system on their roof will require between 15 and 30 400-watt solar panels, assuming they are installing systems between 6 kW and 12 kW in size. 

    That would require roughly 329 and 658 square feet of roof space - before allowing for access and setback requirements, which vary from state to state. 

    Here are average figures for California, Texas, and Florida: 

    400-watt solar panels: number and roof space required
    State System size 400-watt panels required* Space required**
    California 7.33 kW 19 panels 417 sq ft
    Texas 10.32 kW 26 panels 570 sq ft
    Florida 10.75 kW 27 panels 592 sq ft

    *Rounded up

    **Assuming each solar panel is 79.8” x 39.6”

    Do bear in mind that these are average figures, using just three states as an example. The right solar system size for your home will vary based on a variety of factors, including - but not limited to - your energy usage, your utility rates, and the climate where you live. 

    You can find out the recommended solar system size for your home by entering your address in the calculator below.

    Calculate how many solar panels you need for your home

    Key takeaways

    • A 400-watt solar panel produces 400 watt-hours of DC electricity during one hour of direct sunlight.
    • A typical 6 kW residential solar panel system would require fifteen (15) 400-watt solar panels.
    • The best 400-watt solar panels are offered by Canadian Solar, LG, Mission Solar, Silfab Solar, SunPower, and Trina Solar.
    • Expect a solar panel system built with 400-watt solar panels to cost 5-10% more than solar panels built with more common 300-350-watt panels.
    • Using 400-watt solar panels is good for making use of a small roof and for reducing the total amount of equipment needed.
    • Installing a solar power system for your home will generally require between 15 and 30 solar panels that are 400 watts in size, and 329-658 square feet of space.
     - Author of Solar Reviews

    Zeeshan Hyder

    SolarReviews Blog Author

    Zeeshan is passionate about promoting renewable energy and tackling climate change. He developed these interests while studying at beautiful Middlebury College, Vermont, which has a strong focus on sustainability. He has previously worked in the humanitarian sector — for Doctors Without Borders — and in communications and journalism.

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