Best 425-Watt Solar Panels: Cost, Specs & Everything You Need to Know

425-Watt Solar Panel Pricing

While there are some exceptions, the majority of the solar panels available that are rated at 425 watts or higher are generally only available via professional solar panel installation companies. They often aren’t available for DIY installations, so pricing can vary quite a bit from a vendor to vendor. The table below provides average prices per watt for our top solar panels in the 425-watt range.

425-Watt Solar Panel Warranties

Although 425-watt solar panels are more costly than those with lower wattages, they come with two primary benefits: higher module efficiency and lengthier warranties when compared to smaller DIY panels. Solar panel warranties typically cover the equipment itself, installation labor, or the efficiency of the panels over time with a performance guarantee. The best solar panel warranties cover all three and provide peace of mind that your hefty investment will be protected for years to come. The table below provides warranty coverage information for our top panel picks.

Panel Specifications: How Big Is a 425-Watt Solar Panel?

Solar panels vary in size based on the manufacturer, and the dimensions often have to do with the number and size of solar cells in each panel as well as the cell type (usually half cell/half-cut cell or full cell). The average dimensions for a panel with this wattage are 39” by 79” at around 1.4” in thickness. Many panels in this category weigh in excess of 50 pounds, which makes them quite challenging to install as a DIY solar project. The table below provides dimensions and weights for the panels we’ve chosen as the best in this watt class.

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How Much Energy Will a 425-Watt Solar Panel Produce?

One of the most common questions homeowners have about solar panels is how much energy each one will produce. While it might seem like a simple calculation based solely on the wattage, there are many additional factors at play that can lead to significant variances in total power output.

For example, identical 425-watt solar panels will perform differently in areas with varying climates, as cloudy weather can reduce efficiency by more than 75%. Solar irradiance or solar intensity — which we’ll discuss below — is another factor that changes how efficient your panels will be based on your location. The number of hours of sunlight per day in your area can also have a major effect on solar energy production.

Some factors that affect power production that you have some degree of control over include the direction your panels face, the amount of shade on your panels throughout the day, and the brand and efficiency of the panels you choose.

That being said, you can use a generic calculation to estimate how much your 425-watt panels will generate:

1. (average hours of sunlight) x (solar panel wattage) x (75% maximum power production to account for changing weather conditions and lower sun intensity in the morning and afternoon) = your daily watt-hours
2. (your daily watt-hours) / 1,000 = your daily kilowatt-hours (kWh) per panel

How Many kWh Does a 425-Watt Solar Panel Produce?

It’s often not feasible to estimate your solar panel production while taking all of the factors we discussed above into consideration. However, provided you can have a fairly dependable figure for daily hours of sunshine, you can get reasonably close to calculating how much energy your panels will generate with the panel ratings and certifications from the International Electrotechnical Commission (IEC). If we assume you live in an area that gets about eight hours of sun per day, the calculation below should be somewhat accurate:

(8 hours of sunlight) x (425 watts) x (75%) = 2,550 watts per day

(2,550 watts per day) / 1,000 = 2.55 kWh per day

At a maximum of 2.55 kWh per day (which would be considered Standard Test Conditions or STC), you could reasonably expect each panel to produce about 930.75 kWh annually. This number is a good place to start when calculating how many solar panels you need for your solar project. You can divide your total energy consumption for the year — an average of 10,715 kWh in the U.S.1 — by the total production expected per panel.

How Does Solar Irradiance Impact Power Output?

Solar irradiance is a measure of how intensely the sunlight in your area hits the earth or, in the case of a solar system, your panels. The more directly the sun hits your panels, the higher the maximum potential production will be for your location. Due to the curvature of the earth, the states that are best for solar are located nearest to the equator. At latitudes closer to the equator, the sun hits at an angle nearly perpendicular to the earth’s surface, providing the highest intensity. States further north will receive sunlight at a more indirect angle, which limits the maximum production of your panels.

Using a standard solar irradiance measure (expressed in kilowatts per square meter) that you find on a solar calculator for your area is a decent way to account for the sunlight intensity on your property. Remember, this is just one factor that affects potential production, but it is an important one to consider.

Here’s a look into solar irradiance:

Is Panel Voltage Important?

Many people who plan to install photovoltaic modules (PV modules) — especially those moving forward with a DIY solar installation — get caught up in the wattage of their panels and never consider the voltage on their panels’ datasheets. Voltage is easily conceptualized by imagining a container of water with a small pipe leading out of the bottom. When the valve for the pipe is opened, the speed at which water flows out of the pipe (amps) will increase with higher levels of water in the container (voltage). Voltage is sometimes thought of as the force that pushes current to solar batteries or electronic devices and appliances.

Solar panel voltage — including measures for open-circuit voltage (VOC) and short circuit current (ISC) — is important because it determines what your panels can and can’t power. Panels with a lower voltage than the volts required by an electric device won’t power it. For example, a 24-volt panel can charge a 12-volt battery because it has sufficient voltage, but that same panel couldn’t provide enough power to run an electric stove, which typically requires 240 volts. Solar panels can be wired together in a series using branch connectors to increase the maximum system voltage to the inverter so that it’s sufficient to power larger appliances or batteries or even entire homes.

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What Can a 425-Watt Solar Panel Run?

In addition to a minimum voltage, a solar panel must provide ample wattage to power different things around your home, boat, RV, or other off-grid solar projects. In the table below, we’ll include some of the more common household items you should be able to power with a 425-watt solar panel.

What Factors Influence Solar Panel Power Output?

As mentioned above, it’s challenging to estimate accurately how much power your 425-watt solar panels will produce, primarily because there are so many factors that affect power production. Most importantly, varying amounts of sun in your area can mean massive differences in efficiency. You’ll have to consider your average number of daylight hours per day, shading on your panels at any point of the day, and the weather, which can bring clouds and rain that reduce overall efficiency quite drastically.

Your power output will also depend on the brand of the panel you choose and its efficiency rating, how old your panel is (panels lose efficiency as they age), which direction your solar modules are facing, and solar irradiation in your area.

How Many 425-Watt Solar Panels Do I Need?

Determining how many 425-watt panels you need for your solar project will be easiest if you know your annual electricity consumption. You can check your past energy bills for this number, or you can use the average consumption of 10,715 kWh per year for a rough estimate. Next, you can divide this total by the estimated production per panel. Using numbers from our example calculations above, the math is as follows:

(10,715 kWh per year) / (930.75 kWh produced per panel) = 11.51 panels, rounded up to 12 panels

This means a 10-kW solar system would require around 12 425-watt panels. One of the benefits of using solar panels made for residential applications is that you minimize the number of panels — and therefore the weight — you have to add to your roof and maximize production per square foot.

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