How Much Energy Do Solar Panels Produce In A Year? Understanding Average Solar Panel Output

When you're thinking about installing solar panels, you may encounter a well-meaning professional who tells you, "This solar panel will give you 300 watts of solar power."

What does that mean, and more importantly, how does that translate to the solar panel output you may need during a year?

In this piece, we'll answer the main question you want to know: How much energy do solar panels produce in a year? We'll also tell you how solar panel output is rated, the average solar panel energy production and savings and factors that may impact solar panel output. We'll also walk you through the most efficient panels on the market today. Let's get started.

How Is Solar Panel Output Rated?

Solar panel output is rated by the watts they generate. The higher the wattage, the more power you'll get out of your solar system. Residential solar panels usually put out 250 – 400 watts under the most ideal conditions – clean, well-angled, non-shaded solar panels that get peak sunlight usually produce the ideal output for which they are rated.

Wattage Vs. Efficiency

Wattage and efficiency aren't the same thing. Let's go over a quick definition of both:

• Wattage: Solar panel wattage refers to how much a solar panel can produce at peak performance output; that is, under ideal sunlight and temperature conditions. It's calculated by multiplying volts by amperes (amps). Volts represent the amount of force of the electricity and amps refer to the aggregate amount of energy used. In other words, the labeled wattage of a solar panel summarizes the maximum amount of work that one panel can do under the best possible conditions. It isn't an average, nor will it consider factors like night, cloudy skies or weak sunshine when panels aren’t producing their peak output.
• Efficiency: When we talk about the efficiency of a solar panel, we refer to its ability to convert sunlight into usable energy.

It's hard to bring up the concept of efficiency and not go over the factors that affect solar panel efficiency. The type of solar cells you have can also affect the efficiency and power rating of solar panels. In addition, reflectance efficiency and thermodynamic efficiency also go into the mix to determine solar panel efficiency.

The most common solar cells are monocrystalline and polycrystalline:

• Monocrystalline solar cells: Monocrystalline solar cells operate using single-crystal silicone, a much thinner and more efficient material. Monocrystalline solar cells are more efficient because they allow the electrons that generate electricity more room to move.
• Polycrystalline solar cells: Polycrystalline solar cells usually have lower efficiency than monocrystalline solar cells but are less expensive. Manufacturers melt numerous silicon crystals together instead of using a single-crystal approach. Electrons move less freely in this type.

Now, a quick explanation of reflectance efficiency and thermodynamic efficiency:

• Reflectance efficiency: Reflectance efficiency determines the amount of sunlight that is reflected back instead of absorbed by the solar panel. (You want your solar panel to absorb as much as possible.) You can get anti-reflective coatings on your solar panels that help reduce reflection.
• Thermodynamic efficiency: Thermodynamic efficiency refers to the height at which the sun's energy could possibly convert into electricity. Monocrystalline solar cells again increase efficiency by dividing the solar spectrum into tinier areas and raising the efficiency limits.

Average Solar Panel Energy Production

Let's say you have 300-watt solar panels and you live in a very sunny city and state, like Yuma, Arizona. You're likely set to receive 8 hours of sunlight per day in Arizona — or more!

Let's also say you have several solar panels (like 15 panels). In sunny Yuma, your solar panels may produce almost 6 kilowatt hours (kWh) per day.

How does that translate to covering energy usage in your household? Let's take a quick look at the average usage per household in the U.S. The average yearly electricity consumption in 2020 (per residential customer) totaled 10,715 kWh, or an average of about 893 kWh per month, according to the U.S. Energy Information Administration. Homeowners in Louisiana had the highest annual electricity consumption (14,407 kWh per residential customer) and Hawaii had the lowest (6,446 kWh per residential customer).

So, if your home in Yuma generates 6 kilowatts per day, a 6 kW system will generate somewhere between 720 kWh to 900 kWh per month. (Remember, it's hard to end up with absolute figures when you're dealing with weather!)

If you want to express that amount on a yearly basis:

12 months x 720 kWh per month (on the low end) = 8,640 kWh per year

12 months x 900 kWh per month (on the high end) = 10,800 kWh per year

If you want to keep things really simple, think of it this way: Most 1,000-watt solar panel systems mean you buy 5 solar panels of 200 watts each or 10 solar panels of 100 watts each. When you add together the wattage of this type of solar system, you get 1,000 watts, or 1 kilowatt.

Factors That May Impact Solar Panel Output

A few factors impact solar energy efficiency, and a few more impact output. We'll dig into them deeper here.

Panel Size

You might automatically jump to the conclusion that yes, size matters when measuring solar panel output. However, solar technology has improved so much that smaller panels can now absorb more sunlight and produce more energy.  In fact, as engineering continues to improve, more solar cells will continue to fit into smaller areas. Some companies try to maintain smaller solar panel sizes with more solar cells to increase output.

Residential solar panels tend to run about 5 feet long and a little over 3 feet wide. Commercial panels are typically around 6.5 feet long.

Number Of Panels

Adding a lot of panels to your roof is one way to increase your output, but it's important to understand that having a bigger system doesn't necessarily equal more savings. Paying for a larger system may actually negate your energy savings.

Location And Average Amount Of Direct Sunlight In The Area

Shading

When the individual solar cells of solar panels don't get full sunlight (if they are interrupted by shade), they will not work at 100% capacity. If just some solar panels are shaded, the others will work at full capacity, but your system still may not reach its full potential and peak energy output.

Temperature

Believe it or not, solar panels work more efficiently in cooler (and even cold!) temperatures. This means that they'll work as well, if not better, in Wisconsin in the winter compared to Arizona in the winter. As long as photovoltaic solar panels get sunlight, they'll work toward optimum output.

Cleanliness

You may not like the idea of cleaning your solar panels, but it's worth doing because solar panels covered in grime or leaves won't give the photovoltaic cells what they need to work correctly. Clean your solar panels several times a year (and maybe after a lot of wind and dust have blown through) so they are doing their job of converting more solar energy into electricity. There are solar panel maintenance companies out there that can do this for you, so be sure to research your options.

Most Efficient Panels On The Market Today

Which solar panels are the most efficient solar panels for residential solar installations? Let's take a quick look so you know what to buy for your own home.

• SunPower A-Series SPR-A425-G-AC: SunPower has a long and storied history as producing some of the most efficient solar panels anywhere. Specifically, SunPower's A-Series SPR-A425-G-AC has 22.8% efficiency and 425 watts of output.
• LG Solar NeON R Ace LG405Q1C-A6: LG Solar's high efficiency LG NeON R Solar Panel boasts a sturdy design with 405 watts and 60 cells with 22.3% efficiency.
• REC Group Alpha Pure REC405AA: REC Group's Alpha Pure REC405AA panel (with 405 watts and 21.90% efficiency) gives plenty of power despite a touch lower efficiency.

Understand Solar Output Before You Buy

We know your most burning question goes something like this: How much money will solar panels cost me, and how much money will I save if I install them?

To determine this, it’s worth understanding the average solar panel output (and boiling the numbers down to kWh per day) so you learn more about how much you'll save as a household. Gaining a deeper understanding of how much energy a solar panel or solar panel system produces can give you a leg up when considering what to buy. A solar installer can give you a lot of information about solar cells and the amount of sunlight a particular brand of solar panel produces.

For more on how solar panels can save homeowners money, check out our other articles.