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Solar Panel Ratings – Everything You Need to Know About Solar Power Ratings

By Benjamin Strusnik November 10, 2021

Understanding Solar Power Ratings – Everything You Need to Know About Solar Panel Ratings

Most solar panels you will find on the market today are listed according to their power rating in watts. Typically, they will range from 100 watts to right up to 400 watts, but many people are unsure what these numbers actually mean. 

To help you better understand solar panels, we are going to go over everything you need to know about solar power ratings. We will explain the difference between total capacity and actual power output. We will also explain the different types of solar panels you can choose from. From there, we will even recommend some high-quality solar panels and solar panel kits you can choose from to start harnessing the power of the sun right away. 

Once you understand how to properly compare solar panels and other pieces of solar technology, you can start building your own solar power system. By embracing solar power, you can decrease the cost of your monthly electricity bills, reduce your dependence on the utility companies, and do your part to protect the environment and improve local air quality.

What is the Wattage Rating?

When you look at solar panels, most modules are rated between 100W and 400W, usually in increments of at least 50W. What this wattage rating represents is that particular solar panel’s expected power production in one hour of ideal conditions, meaning direct and unfiltered sunlight and perfect weather conditions. 

As you would expect, the higher the solar panel is rated in watts, the more powerful it is. These higher efficiency solar panels can produce more DC electricity in the same amount of space as similarly sized solar panel with a lower power rating.

The Cost:

In almost every situation, the higher the watt rating, the more expensive the solar panel will be, which explains why the overall wattage of a solar power system is usually a good indicator of how expensive it was to assemble.

That being said, there are some exceptions to this general rule. For example, some solar panels are more expensive than others because they have useful features, such as a folding design for portability, built-in support legs, and waterproof exteriors. You can also find miniature low wattage solar panels that were specifically designed to pair with portable electronic devices while hiking and camping. However, these relatively expensive, travel-friendly solar panels are not what you would be looking for if you were planning to assemble a residential grid-tied or hybrid solar power system. 

How is Wattage Calculated? 

In simple terms, wattage is calculated by multiplying the total volts and amps a solar module can produce. The volts, or voltage, represents the force of the electricity that is generated by the solar panels when they are operating at their full potential. The amp rating refers to the flow rate of that electricity. When electrons flow from a high voltage area to a low voltage area, that flow is measure in amps. 

Basically, wattage refers to the energy produced when flowing electrons encounter resistance. This energy is measured in watts and is always equal to volts multiplied by amps, or Volts x Amps = Watts.

In other words, when sunlight hits a solar panel, voltage and current are produced. This current, pushed by voltage, flows through wires in the electrical system and has to work when it encounters resistance, this work is measured in terms of watts. 

Do Solar Panels Always Produce the Watts They are Rated for?

Unfortunately, the wattage rating of a solar panel only refers to the amount of power it can produce while operating in ideal conditions. In reality, the actual power output of a solar panel will depend on a number of factors, including its positioning, the components the solar panel is connected to, the number of peak sun hours it is exposed to, and environmental factors, like shading and cloud coverage. 

Sun Hours:

One of the most important factors you will need to analyze to understand how much power your solar panels will actually generate is the number of sun hours they will be exposed to per day.

Sun hours refers to the number of peak sun hours you typically get in your specific geographic location. The average number of peak sun hours varies rather significantly across the country and around the globe.  This means the amount of sunlight and the intensity of that sunlight your solar panels will be exposed to will depend on where you live. 

While the sun might be shining throughout the day and it may seem like you get 12 solid hours of daylight, you likely only receive around four or five peak sun hours. The term ‘peak sun hours’ is actually used to describe hours where the intensity of the sunlight is at its highest, not just hours where it is bright enough to see outside. Typically, a peak sun hour is defined as an hour in the day when the intensity of the sunlight reaches an average of 1,000 watts per square meter. 

Other Factors That Impact Performance:

Seasonal changes play a major role, as the Earth’s tilt alters the amount of sunlight an area receives throughout the year. The peak sun hours chart displayed above actually just refers to the average number of peak sun hours each part of the United States receives. In reality, solar panels can provide far more power during the summer and about 25% to 50% less during the winter months. 

The direction and positioning of the solar panels also plays a major role. In general, you will want to face your solar panels in a southward direction that is not shaded at any point throughout the day. 

The overall efficiency of your solar power system will also impact its power rating. This is why it is so important to match your solar panels with an appropriate power inverter, charge controller, and battery bank. Making sure everything works together efficiently will help prevent the unnecessary loss of power through the system itself.

Monocrystalline and Polycrystalline Solar Cells

There are two main types of solar cells used in solar panels – monocrystalline and polycrystalline. The type of solar cells used within a solar panel can also impact the efficiency and power rating of that particular solar panel.

Monocrystalline solar cells use single-crystal silicone. Monocrystalline solar panels are generally considered premium products, as they are more efficient and can be made much thinner. With a single crystal cell, the electrons that generate a flow of electricity have more room to move, which improves the overall efficiency. 

Polycrystalline solar panels usually have lower efficiencies, but they are also less expensive. Instead of using a single crystal of silicon in the solar cells, manufacturers melt numerous silicon crystals together to form a wafered-style cell. With more crystals in each cell, there is less freedom for the electrons to move, which reduces efficiency.

Efficiency Ratings: 

While power ratings are designed to indicate the power potential of a solar panel, efficiency ratings are another important indicator of the panel’s overall quality. Efficiency ratings continue to improve, but currently, they tend to range between 15% and 20%. 

The more efficient the solar panel is, the more sunlight it can convert into useable electricity. When shopping for solar panels, keep an eye out for the efficiency rating, as the higher the percentage, the better your solar panel will perform and the more often it will be able to produce electricity at a rate close to its power rating. 

Shopping for Solar Panels

When shopping for solar panels, there are quite a few different options. The first step you will want to take is figuring out how much solar electricity you actually need. Our Solar Watt Hour Load Calculator can help you determine how much electricity you actually need to power your electrical devices and appliances, which will help you determine the number and types of solar panels you will need to satisfy those power needs.
By shopping our Complete Solar Panel Collection, you will be able to choose from a wide range of solar panels with a variety of power ratings. You can also read our comprehensive 300 Watt Solar Panel Guide, which will tell you everything you need to know about 300W solar panels.

Solar Panel Kits:

One of the easiest ways to get started with solar power is to purchase a complete solar panel kit. Not only do these kits contain efficient solar panels, they come with all of the other pieces of solar equipment you need to start accessing clean solar electricity. In one convenient and affordable package, you get solar panels, a charge controller, power inverter, deep cycle solar battery, and all of the solar cables and connectors you need to wire everything together.

You can shop our Complete Collection of DIY Solar Panel Kits and find a kit that can meet your specific power needs. For those looking for something a little bit more specific, our Renogy Solar Kit Collection offers a variety of solar kits that have been assembled using just Renogy components. Given that Renogy is a reputable solar brand that is known for offering high-quality solar equipment at competitive prices, it is no surprise that these kits are an extremely popular choice. For beginners, we often specifically recommend the Lion Energy 400 Watt Beginner Solar Panel Kit. The kit comes with everything you need to start generating clean solar electricity right away. At one low price, you get a deep cycle solar battery, a power inverter, an efficient and foldable solar panel, and a high-performance charge controller.

For those with greater power needs, the highly portable 500 Watt Complete Titan Solar Generator Kit presents an outstanding deal. In one convenient package, you get the all-in-one Titan Solar Generator, which contains a built-in 2,000Wh battery, power inverter, and charge controller, as well as five 100W solar panels (check 100 watt solar panel datasheet). You also get all of the solar cables and MC4 connectors needed to get your system running.

You might be interested in our next guide - 100 Watt Solar Panel Equals How Many AMPs.

Final Words 

While it is always important to keep an eye on power ratings and efficiency ratings, they are not the only factors that will determine how much power your solar power system can generate. Pay attention to the number of peak sun hours you receive in your area, as well as other factors, like the angle and direction you use to install your solar panels on.

There are many things you can control to make sure your solar panels are working at their highest potential. As always, you if you have any questions about solar panel power ratings, or any general questions about solar power, you can always reach out to us at any time!

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