400 watt and 500 watt solar panels: Are they right for you?

If you’re thinking about installing solar panels on your roof in 2024, it’s more than likely you’ll be buying 400 watt (W) panels. As solar technology advances, the wattage of a typical solar panel has steadily been increasing. Today, most panels you'll find on a residential home are 400 W, which is almost double the wattage of the first solar panels that came on the market. You can think of the wattage of a solar panel as the amount of power it can generate in a certain amount of time under ideal conditions. The higher the wattage, the more power a panel produces.

Although the industry now also produces 500 W solar panels, it’s unlikely you’ll need that much wattage per panel to power your home. The most common uses for 500 W panels are usually commercial buildings or utility-scale projects.

We’ll walk you through what you need to know about both 400 W and 500 W solar panels so you understand the pros and cons of each panel size, and when it makes sense to use either one.

A 400 W solar panel does what it sounds like – one panel produces an output of 400 watts of electricity, which yields approximately between 1.2 and 3 kilowatt hours (kWh) daily. How much electricity your panels actually generate on a day-to-day basis depends on a few key factors such as how much sunlight they get, your geographic location and the angle your panels are tilted at. What season it is also plays a role in how much electricity your panels will generate - in the summer their output will be much higher than the winter because they’re exposed to more hours of sunlight on a daily basis.

On average, a home in the U.S. consumes about 30 kwh every day, or 900 kWh per month. While 400 W panels can be used for commercial projects, you’ll see them most frequently on people’s homes rather than big buildings.

The 500 W solar panel was designed to meet the solar energy output needs of medium and large solar systems using fewer panels, which increases efficiency and lowers costs. Solar panels used to be much smaller than 500 W (just 300 W or less as recently as a few years ago), so they represent a big technological improvement.

There are two ways to increase the power of an individual panel:

1. You can make it bigger (i.e., go from a 60-cell module to a 72-cell module that takes up more space).

2. You can increase the overall efficiency of the solar panel (how well it captures sunlight) by improving the manufacturing process of its silicon cells, the solar panel itself, or both.

Many 500 W panels are manufactured using half-cut solar technology, which leads to high efficiency and durability with a half-cell. As are most solar panels today, 500 W panels are always monocrystalline, which is a more efficient material than polycrystalline.

Although they aren't necessarily practical for homeowners, the creation of 500 W solar panels was a significant milestone in the solar industry because that level of panel efficiency and power output from a single solar panel was unheard of even five years ago.

An individual 400 W or 500 W solar panel typically costs anywhere from $250-$400, according to EnergySage data. The cost of the electricity they produce can vary widely from 20 cents per watt to $1 per watt, depending on the quality of the panels you purchase.

Most residential solar systems nowadays use 400 W solar panels, although 300 W panels are still relatively common as well. According to EnergySage data, the most frequently quoted solar panels are around 400 W.

In addition to residential properties, 400 W panels are well-suited for powering RVs, boats, and other off grid devices. A single 400 W panel can power an RV or boat for a significant amount of time.

500 W panels are still relatively rare in residential installations. Two of the main differences between a 400 W and 500 W panel are that 500 W panels are designed primarily for larger scale installations, meaning they're physically bigger than typical residential panels. 500 W panels are also bifacial, which means they can collect sunlight from both the front and back of the panels, increasing the overall amount of electricity produced. Bifacial panels are less frequently installed in residential applications.

Both 400 W and 500 W solar panels provide significant savings, especially when paired with a solar inverter, charge controller, solar battery, or other type of energy storage.

For example, a 20-panel installation of 500 W solar panels (10 kW system) will produce enough electricity to offset about a $200 monthly electricity bill, depending on where in the country you live. On the other hand, a 20-panel installation of 400 W panels (8 kW system) can offset a $160 monthly electricity bill.

Something to keep in mind when you install solar panels is your future energy use. If you're thinking about buying an electric vehicle or installing a heat pump, then you may want to increase the number of panels you put on your roof even if the amount of energy they'll produce exceeds your existing needs. However, some utility companies won’t always allow you to install a system that generates more power than you currently need, so it's important to confirm whether or not yours will allow you to do so.

The number of solar panels you need to install depends on how much electricity you want to generate and how much roof space you have available to mount solar panels. The table below compares different-sized solar panel systems using the number of 400 W solar panels that are needed for each system size. The number of 400 W panels is rounded to the nearest panel.

To calculate how many solar panels you need, simply divide your annual electricity usage by your production ratio and then divide that number by the wattage of your solar panels. Let's use an example: the average U.S. household uses about 10,800 kWh of electricity every year, according to the U.S. Energy Information Administration (EIA). If we assume an average production ratio of 1.4, here's how to do the math:

System size/production ratio/panel wattage= number of panels

10,800 kWh / 1.4 / 400 W= 19 panels

*Number of panels needed, rounded to the nearest panel and assumes a production ratio of 1.4

So you can see that installing only five 400 W solar panels, which would produce roughly 3,000 kilowatt hours (kWh) of electricity, isn't enough to cover the amount of energy a typical single-family home uses. You'll most likely need to install anywhere from 15-20 panels to offset your electric bill, assuming you use about 10,800 kWh of electricity annually like the average household does.

*Number of panels needed, rounded to the nearest panel and assumes a production ratio of 1.4

400 W solar panels are more space-efficient compared to their older, lower wattage counterparts that used to be the industry standard. With 400 W panels, a typical roof on a single-family home will likely have enough room for the number of panels you need to offset the majority of your electricity costs.

Most people usually end up installing anywhere from 15-20 panels. However, if you have a small roof or don't want to put solar panels on your roof, consider a ground-mounted solar system instead.

If you're considering going solar, you can get multiple quotes from pre-screened installers by signing up on the EnergySage Solar Marketplace. If you already know what kind of solar equipment you want, you can note your preferences on your account so installers can give you quotes for those specific products or brands. If you're simply looking for a quick estimate for how much money solar can save you, try our Solar Calculator.