October 10, 2019
If you’re thinking about installing a solar energy system, or are just curious about what solar can do, you’ve probably wondered how much one solar panel can produce. Whether it’s rows and rows of panels on a large warehouse or just a few mounted to your neighbor’s roof, are they producing enough electricity to cover their whole electric bill, or just a few light bulbs?
While how much one panel produces depends on a few factors (we’ll go over that in a little bit), even giving a general answer comes down to the panel you chose. Each solar panel is tested by its manufacturer to determine how much electricity it will produce in the best-case scenario, or peak sun (also known as Standard Test Condition or STC). This number is the solar panel’s wattage or power rating.
Most solar panels used in commercial or residential solar have wattages within the high 200s to the low 400s. While more efficient solar panels mean more power, they also often cost more. Your solar installer will help you select which wattage of panels are best for your project’s payback.
That wattage is often the number that’s in a specific panel’s name, so a panel like the Axitec 380W Monocrystalline Solar Panel is a 380-watt solar panel.
Here’s a specific example. At STC, a brand new, 320-watt solar panel should produce 320 watts. If it does that for an hour, you’ll get 320 watt-hours, or enough electricity to power an efficient refrigerator (say, one that uses about 1 kilowatt-hour or kWh each day) for about 7.5 hours.
However, STC isn’t often duplicated in real life, due to passing clouds and temperature fluctuations (solar panels actually perform more efficiently when it’s cooler). Even if you live in a very sunny area, your panels won’t perform on that same level in the real world for a very long period of time.
Why not? Let’s take a look.
Unfortunately, solar panels won’t perform the way they do in lab-controlled STC in the real world. Between how the solar panels are installed, the weather in your area, and the other equipment that makes up the solar system, your panels will produce less than the wattage rating.
But don’t let these factors scare you away. Your estimates from reputable, qualified solar installers will take all of these into consideration. That means the energy production estimates, ROI, and payback for your solar panel system should be pretty accurate, regardless of the installation method or local weather.
Regardless of the solar panel you go with, how much energy it produces is dependent on how much sunlight reaches the panels. Whether it’s clouds in the sky that block sunlight from the surface or snow or dust that cover the solar panels, the weather is a big factor in that.
Solar installers use historical data on the local weather patterns to provide as accurate an estimate of electricity production as possible. That number is worked into your system’s payback, giving you a realistic picture of what your solar investment can do. So if you live in an area that gets a lot of clouds, but the ROI and payback look good, rest assured your solar proposal reflects the entire picture – not just a sunny one.
The tilt of the solar panels is the degree at which they are installed in relation to level. In most cases, to optimize production, a panel’s tilt will match the latitude for the location. The closer to the equator you are, the flatter that angle will be. However, small variations don’t impact production in a big way. If you’re looking to install solar panels on your roof but the roof’s pitch doesn’t match the latitude of your location, the difference in electricity production will likely be minimal.
Orientation is the direction the faces of your solar panels are pointed in relation to north. In most cases, true south will maximize the panels’ exposure to the sun, meaning more electricity is generated. But panels that are positioned east or west still get a fair amount of exposure and might reduce production around 15% (depending on the tilt). Thanks to dropping material costs, this can be easily remedied by adding a few extra panels to make up for any lost production.
Shade can come in all shapes from all sources. Be it a tree over the array or a tall neighboring building, if it’s in the panel’s way of the sun, it will produce fewer watts. Thankfully, solar installers are able to use a handy tool called a solar pathfinder to analyze shading in an area and work that into the production estimate.
The amount of energy your solar panels produce depends on all the equipment that make up your solar power system.
The power tolerance of a solar panel measures how much electricity the panel can produce in relation to its wattage rating. Some panels have a negative rating, which means they may produce less electricity than the specified wattage at STC. At Paradise Energy, we only use panels with a positive power tolerance, ensuring that won’t happen to your panels.
Degradation is a normal and unavoidable part of solar panels. Just like so many other things, solar panels don’t perform at 100% for their entire life and then just stop working in year 30. Instead, solar panels, at a very slow rate, produce less electricity as they age. This process is called degradation.
While each year your panels lose a small percentage of power output, your solar installer should account for this in their estimates, meaning it isn’t a hidden force eating away at your payback. And you won’t have to worry about getting a bum panel that degrades more quickly than it’s supposed to. Each solar panel comes with a performance warranty that guarantees the efficiency won’t drop below a specific percentage.
Anytime two things connect, there’s a chance for a loss in efficiency. Solar panels, even though they’re rated for the same voltage and current, may experience a small loss, depending on the type of inverter you select. Microinverters and power optimizers (also known as module-level power electronics) work on a panel-by-panel basis and can drop loss to 0%. The industry standard for string inverters is around 2%.
An inverter is what converts the DC power produced by the solar panels to AC power, which is what’s used by your homes and businesses. This essential part of solar systems, however, introduces the potential for a small loss in efficiency.
Small amounts of electricity can also be lost through heat and voltage drop as it travels from the panels to the utility meter. However, properly sized wire and connections reduce how much is lost. Other factors, such as the distance from the inverters to the utility meter may also contribute to lost electricity.
If you’re wondering how many solar panels it would take to zero out your electric bill, or how many square feet of solar panels it takes to cover that bill, check out the video below, or read our blog.