Best 400-Watt Solar Panel (2023)

400-watt solar panel system on roof

The 400-watt solar panel is quickly becoming the preferred size of solar panels for homes, businesses, van-lifers, and RVs. Why? Because they can produce some of the most efficient energy outputs for the least money of all the solar panel sizes.

Generally speaking for solar panels, bigger is better because you get the most energy per surface area. The largest solar panel size available is 500 watts. However, 400-watt solar panels are the most popular because they offer reduced risk in the improbable situation that a panel breaks and they typically fit more areas and shapes (roof shapes, vans, RVs).

This article answers some of the most common questions surrounding 400-watt solar panels and recommends our favorites.

400 watts more than what you are looking for? Check out our articles on 300W, 200W, and 100W solar panels.

Our Top 3 List

Best Overall
Best Value
Best Portable Solar Panel

What to Know Before you Buy

The key considerations when deciding what solar panel is right for you are:

  • Cost – because you likely aren’t looking to blow the bank. The cost typically depends on durability, efficiency, look, panel type, and where they are made.
  • Warranty – the standard for warranty is 25 years. Typically, this warranty is for the integrity of the panel, and a guarantee on the percentage of power output at 25 years (e.g., 87% guarantee at 25 years). Our favorite warranty provider also offers a 25-year labor warranty meaning they cover the costs of replacement installation.
  • Size – is important when you are working with a tight space or roof/mounting angles. If you are doing a self-installation… measure twice and buy once.
  • Efficiency – highly efficient panels offer more energy in a smaller area. However, they are typically more costly. So if you are not short of space, you may wish to opt for a less efficient panel to save on cost.

We have included these details for each of our favorite panels below.

How much power does a 400-watt solar panel produce?

The amount of power a 400 watt solar panel produces is a bit of a tricky question with no straight answer. Power outputs for solar panels are based on the maximum amount of output at that moment. So a 400 watt solar panel is capable of outputting 400 watts at that moment. 

But! That is under ideal conditions only, and you rarely have perfect conditions. So if you are looking to have power constantly and aren’t connected to the grid, you may wish to look into battery storage. Potential things that may reduce your maximum output include:

  • Shade (e.g. clouds or trees)
  • Orientation (i.e., how directly the sun shines on your panel)
  • Panel age
  • Time of day
  • Temperature

What can a 400-watt solar panel run?

As a general rule; movement and light require less electricity, and heat requires more electricity. So if you are looking to heat the space, you still may want to look into a safe fuel source to save on the number of panels you need.

For example, if you are asking “will a 400-watt solar panel heat my van?”, the answer is that it might not be super efficient at it. Heaters typically take 1500 watts. So you would either need to store that energy in a battery and have limited time running the heater, or you may need multiple panels.

If you are asking “can a 400-watt solar panel run a refrigerator?” the answer is likely yes. However, you will likely need battery storage, little shading and some good orientation.

Here are some examples of the energy it takes to run typical items that you may be wishing use your solar system with:

How big is a 400-watt solar panel?

The typical height of a 400 watt solar panel is between 60 inches and 100 inches.

The typical width of a 400 watt solar panel is between 40 inches and 50 inches.

How much does a 400-watt solar panel cost?

Solar panels are priced on a per-watt basis. The typical price for a 400 watt solar panel ranges between $2.25 USD/Watt and $4.50 USD/Watt.

This metric is used because it shows the cost savings that you receive from using a 400 watt solar panel vs. a 100-watt, 200-watt, 300-watt, or 500-watt solar panel.

Generally, for one 400 watt solar panel, you are looking at spending $900.00 USD to $1,800 USD. However, if you are buying in bulk, or buying from an installer, you are likely to receive a discount on this pricing.

Is a 400-watt solar panel good for my project?

Depends. If you are asking “Is a 400-watt solar panel enough for RVs” or “Is a 400-watt solar panel enough for my house?”

Generally, a 400-watt solar panel is going to give you the best bang for the buck when it comes to efficiency (the amount of power per area). However, 400-watt solar panels are larger, and if one breaks (unlikely, plus warranties) they are more expensive to replace.

So if your project has lots of room, like the roof of a house, or an RV, I would say they are a perfect option. However, if you are worried about space, you can get some good efficiencies from 300-watt solar kits, 200-watt solar panels, and 100-watt rigid solar panels.

How many 400-watt solar panels do I need?

Honestly, this is a really complex question. If you are looking to put solar on the roof of your house, then I would recommend talking to a credible home solar panel installer. They are skilled in completing energy models to estimate your usage and production.

Let’s guide you through what you have to consider:

  • A single 400-watt solar panel produces a maximum of 400 watts per hour. This doesn’t mean it’s always producing 400 watts. So you will likely need more than you think.
  • Additionally, you are going to have to consider the time of year you will be using power to account for sun angles and weather.
  •  Shading and the direction the panels face will impact them. Ideally you want to face directly towards the sun and have no shading.
  • Battery storage is useful because you don’t have to be producing power when you want to use it. I would recommend battery storage if you are using the panels for an RV, van, or off-grid house. I would recommend no batteries for a grid-tied solar house to save money and have less environmental impact.

If you are interested in getting a more exact measurement of how much energy you need to produce, you could consider getting an energy monitor. Energy monitors will track your real-time, daily, monthly, and yearly energy usage, including the amount of energy each appliance uses.

If you are looking for something relatively simple we recommend the  Sense Home Monitoring System. If you want to find out detailed energy use for certain appliances we recommend the Emporia Energy Monitors.

Read More: Our Top 7 Tips for Building a Net-Zero Home

Our Top 400-watt solar panels

Best Overall

1. SunPower


Cost: ~$3.25/W | Warranty: 25-years | Size: Variable | Efficiency: 22+%

SunPower is our favorite company if you are looking for a full home solar system. With good warranties, long-standing industry trust, and great efficiency it’s easy to see why they are our favorite.

  • 25-Year Warranty for product and performance. Up to 40-Year Warrant for certain products.
  • Generally highest-efficiency 
  • USA and Canada wide
  • 30-years of experience as a supplier
  • Available compatible solar batteries
  • Countless installers
Final Verdict

SunPower is a go-to brand for solar panels. A key feature of having a good warranty is knowing that a company has been around and will be around long enough to be able to provide its warranty 25 years from now. If you are looking for lots of power in a tight area, give them good consideration.

Best Value

2. CanadianSolar

HiKu dual cell Perc CS3n400

Cost: $2.75/W | Warranty: 25-year | Size: 76.4″ x 41.3″ x 1.4″ | Efficiency: 20.9%

CanadianSolar is almost always some of the best value in solar. You can’t go wrong with this their long-standing record as a solar panel producer, good warranties, and great costs.

Additionally, the HiKu dual cell Perc CS3n400 has built-in shade tolerance and durability technology for impact protection, and reduced degradation, wind, and heavy snow loads. Our only downside to this panel is its lower efficiency rating, meaning it might not be great if you are looking to produce lots of power in a small space.

  • 25-Year Warranty for product and performance
  • Operates on 6 continents
  • 22-years of experience as a supplier
  • LID/LeTID mitigation technology for 50% lower degradation
  • Snow loads up to 5400 Pa
  • Wind tolerance up to 2400 Pa
Final Verdict

If you are looking for a durable panel at a great price and have no space limits, then CanadianSolar’s HiKu dual cell Perc CS3n400 fits your needs perfectly.

Best Portable

3. EcoFlow

400W Portable Solar Panel

Cost: $3.43/W | Warranty: 1-year | Size: 42.0″ x 94.1″ x 1.0″ | Efficiency: 22.4%

The EcoFlow 400W Portable Solar Panel is a pretty impressive piece of hardware. It is essentially the only portable solar panel capable of reaching such high power output.

EcoFlow does report that the realistic energy output of this unit is 350W in near-perfect weather. But, who can really complain when you can carry and assemble an energy system capable of charging 35+ phones in the middle of nowhere?

  • 1-year warranty
  • High-efficiency
  • Included carrying case which doubles as a kickstand allowing you to get better orientation in the field
  • High power output for a portable solar panel
  • Eco-conscious packaging
  • 35 lbs
  • Durable enough (IP68) to withstand dirt, sand, and limited submersion
  • Compatible with certain batteries
Final Verdict

This an amazing option for a remote-use 400-watt solar panel. With good durability and waterproofing you can tell EcoFlow designed this unit to be field used and tested.

Additional Resources

Frequently asked questions on solar panels

Amps are not directly connected to watts alone. They are also dependent on volts. So answers may vary for the panel you pick. 

Here’s how to calculate amps:

Watts (Power) / Volts (Voltage) = Amps (Current)

Generally, the answer is yes. You should clean your panels to ensure you are getting the most out of them.

Frequency of cleaning is dependent on climate. If there is excessive dust, dirt, smog, or leaves in your area then you may have to clean your panels more often. However, if you are in an area with hard seasonal rains then you may not have to do it often because the rain will do it for you.

The amount of power a 400 watt solar panel produces is a bit of a tricky question with no straight answer. Power outputs for solar panels are based on the maximum amount of output at that moment. So a 400 watt solar panel is capable of outputting 400 watts at that moment.

However, this output is negatively impacted by shade, time of day, direct angle to sun, age of the panel, dirt, and temperature.

Tricky question. Our recommendation is to email your panel supplier or electrician (make sure they are experienced with solar). But, let’s run you through it anyways, so you know what details to chat with them about.

There are different types of inverters (string inverters, microinverters, and power optimizers with central inverters). All of these have compatibility requirements and different specifications, so may not be compatible with your chosen 400 watt solar panel.

The inverter you need also depends on what you plan on doing with the solar panel. There are two types of current; Alternating Current (AC) and Direct Current (DC). Some electricity grids or objects in your house use DC and some use AC. The current type of your appliances and grid may change what inverter you need.

The size of inverter is important because large ones are more costly and inverters that are too small for your load may be damaged if you exceed their maximum power output. So knowing what you plan on running with the panel is important to picking the right inverter as well.

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