Solar Panel Watts per Square Foot
Updated: July 10, 2023
There are many different types and sizes of solar panels available on the market and choosing the one that meets your solar panel watts per square foot requirements can be challenging.
When looking into it, the efficiency of a solar panel is obscured with scientific equations and jargon which can be cumbersome to the everyday RV or homeowner.
The answer to how much energy a solar panel produces is not an exact science and calculating the wattage of your solar panels depends on many factors.
This article simplifies the process of calculating solar panel wattage per square foot and provides you with the knowledge and tools to determine the size of solar panel you need.
Understanding Solar Panels
Before calculating the watts per square foot of solar panels, it's vital that you have a basic understanding of what a solar panel is and how it’s affected by various factors.
What Is a Solar Panel?
Defining a solar panel and what it does can lead to large quantities of scientific jargon ending in confusion.
In a nutshell, a solar panel is a mechanism in which energy from the sun (solar energy) is converted into electrical energy for everyday use.
This electrical energy is then stored in a battery, such as a LiFePo4 Battery, which in return powers the appliance.
Calculating Solar Panel Output
There are many ways to find the properly-sized solar panel for your home.
The average residential solar panel can produce 250 to 400 watts per hour.
The following method is a rough method of calculating the output of a solar panel.
The simplest way to calculate the power output per square foot of your solar panel is division. For example, the Bluetti 120W Foldable Solar Panel produces a peak of 120W and measures roughly 9.5 square feet.
This works out to 12.6 watts per square feet for the solar panel. Next you need to figure out the energy requirements for your home.
List the Appliances
The first step to the calculation is to make a list of all the appliances and objects you intend on running through the solar panel.
Each appliance you use has a power consumption rating label, either printed on it or on a sticker attached to the device or its charger.
On this label, you can find the output rating for the device which will either be listed in watts, volts and amps, or milliamps.
Ultimately what you are trying to find is the wattage of the device.
List Possible Usage of Each Appliance
Once you’ve compiled your list, you need to establish how long you use each appliance per day.
You want to track the hours per day. For example, you might use your oven for 1 hour per day and your fridge for 24 hours per day.
Calculate the Watt Hours per Day
This step shouldn’t intimidate you. Simply take the hours per day of the appliance and convert it into watts.
To do this, take the output wattage and multiply it by the hours per day the device is used.
For example, let's say you have 2 phone chargers at 85 watts each, and you intended on using them for 4 hours per day.
Your calculation for the watt-hours per day of these chargers is 85 x 4 x 2 which gives you 680 watt-hours per day.
You have to do this equation for each appliance on your list.
Calculate the Total Watt Hours per Day
To calculate the total watt-hours per day, simply take all the values obtained in the previous step and add them together.
This number represents the total watt-hours use daily.
Calculate Solar Needs
This calculation is technical and can be very difficult to understand.
Luckily, there are many solar calculators available which provide a step-by-step explanation.
For accurate results and time-saving, we recommend an online solar calculator to determine your solar needs.
The solar calculator will require you to insert the figures you calculated in the previous steps to give you the number of panels you need.
The number of watts per square foot forms part of the result that the solar calculator provides you.
Factors Affecting Solar Panels
To understand the calculation of solar panel wattage, you should familiarize yourself with some of the factors that affect the efficiency of solar panels.
Heat is often a confusing topic when it comes to solar panels.
While an area with consistently high temperatures can be an indicator of high levels of solar energy, temperature itself is not a direct factor that influences an increase in wattage.
In fact, high levels of heat for long periods can have an adverse effect on a solar panel's lifespan because lower temperatures lower the resistance of a circuit.
Therefore, when deciding on the prime area to place a solar panel, an area littered with shade and another baking in heat will not be ideal locations.
Contrary to popular belief, a solar panel can operate with high efficiency on cloudy days and doesn't require a full day of direct sunlight every day.
This phenomenon is due to the wide spectrum of light provided by our sun.
In basic terms, there are forms of light in our spectrum that are visible to the human eye and others, such as ultraviolet, which aren`t.
Therefore, what might appear to us as a cloudy, non-ideal day for solar panel efficiency, might actually be a great day for gathering solar energy.
It should be noted that each solar panel’s installation needs are unique due to the location of your home in relation to the sun.
As a general rule, solar panels should be installed facing due South for maximum solar panel voltage output.
After all, it would be nonsensical to install a solar panel perpendicular to the ground, so that only one-half of the panel receives maximum light at any given time.
Are Solar Panels a Long-Term Benefit?
One of the most searched questions is whether a solar panel is an investment for a long or short period.
In other words, how long does it take for a new solar panel to be replaced and what is a solar panel's lifespan?
The lifespan of a solar panel is dependent on the factors mentioned above, the quality of the panel, and due care and maintenance of the panel.
The average lifespan of a solar panel is roughly 25 years, which is the standard warranty for the majority of panels available today.
A good way of determining the lifespan of a solar panel is finding out when the panel’s inverter needs to be replaced, which is usually between 10 and 25 years.
Thus, spending on the quality of the panel one selects for purchase, it's more than reasonable to suggest that solar panels are indeed a long-term investment.
Energy Produced by Solar Panels
One of the key questions for any prospective solar panel buyer is how much energy does a solar panel produce?
Once again, the energy a solar panel produces depends on the factors like its quality, location, and size.
Bear in mind that when discussing the wattage produced by a panel, the correct unit of measurement is kilowatt-hours.
The average residential solar panel is roughly 66 x 44 inches and each solar panel produces, on average, 30 to 40 kilowatts per hour.
To put this in perspective, 1 kilowatt-hour is enough to power an electric car for at least 3.5 miles.
Improving Solar Panel Efficiency
Increasing a solar panel’s efficiency can become a cumbersome and obsessive task if you're not happy with your solar panel`s output.
Firstly, the size of the solar panel in relation to the object you're trying to power. You’re not going to be able to run your entire house off of one, 3-foot solar panel.
The ideal location for any solar panel is somewhere well-lit and unobstructed where the panel can receive direct sunlight.
Lastly, panel maintenance is something that’s often overlooked that has a huge effect on the efficiency and power output of your solar panel.
Choosing the Right Solar Panel
The most important aspect to consider when choosing a solar panel is the watts per square foot required for your needs, which will be evident from the values given by the solar calculator.
There are even off-grid solar-powered systems available specifically for those looking to power a household or appliance network outside of the daily traffic of a town or city.
For camping enthusiasts, RV owners, or those constantly on the move, a quick and easy solution to solar energy can be portable solar panels.
Solar panel users have a variety of needs that they need filled, so manufacturers have made solar panels to fit those niches. Take the time to understand your situation and make sure to get a solar panel and generator kit that suits your needs, otherwise, you’ll be spending extra money on features you don’t need.
A solar panel that’s perfectly suited to a home or RV in New York City might not necessarily suit that of a person in Las Vegas for reasons such as the weather and daily light available.
The watts per square foot of a solar panel will always vary depending on the factors listed above, but the solar calculator will assist greatly in this regard.
Finally, prices will change in relation to things such as size, quality, and type of the solar panel used, so choosing the panel which provides the correct watts per square foot is vital.
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