Sizing Solar Panels for Your Solar Power System – Discover the Basics
When it comes to sizing a solar power system, there are three main things that you need to look at – sizing your battery, inverter, and your solar panels. We already explained how to size battery capacity for your system, and later we’ll show you how to size your inverter, but today’s lesson is all about sizing solar panels for the needs of your system.
We’re going to break down the process so you can discover just how easy it is to properly size a solar panel array. Just like all of our previous lessons, we’re going to make this as beginner-friendly as possible.
So, let’s dive in!
Step One: Understanding Your Peak Sun Hours
Before you just start adding solar panels to your online shopping cart, you need to determine the number of peak sun hours you have in your area.
This will differ based on where you plan on building your solar power system. If you live in Arizona, your sun hours will be quite different from those of someone living in Minnesota. However, on average, most places in the U.S. mainland receive about 3 to 5 hours of peak sunlight per day, so the variation isn’t anything too crazy.
If you’re unfamiliar with the term, peak sun hours is a name for the full hours of the day where the sun is high in the sky, allowing solar panels to be at their most productive. Hours where the sun is low on the horizon during sunrise or sunset don't count as peak sun hours, as your solar panels won’t be able to generate the same amount of energy during them. Sure, they might be able to generate some solar power, but these hours shouldn’t factor into your calculations.
To properly size your solar panel array, it's crucial to research the peak sun hours for your area. Jackery offers a pretty handy chart that makes it easy to find your peak sun hours by state or by ZIP Code. Look up your area and make a quick note of how many peak sun hours you can reasonably expect on a typical day.
Step Two: Determining Your Solar Panel Wattage Needs
For this step, you’ll need to determine how much wattage you need your solar panels to be capable of generating.
This will rely on the size of your battery bank, which is why we previously broke down how you can size a battery bank for your solar power system. If you’re unsure how big your battery should be, or you’re not sure how to size a battery bank, just go back and watch our video: Sizing Battery Capacity for Your Solar Power System.
To make things easier to follow, let’s pretend your system has a 10,000 Watt-hour (Wh) battery bank. The goal in this example scenario is to fully charge this battery bank within one day. This would ensure that you have enough power for your needs, even on cloudy days where there is less sunlight available to charge your battery.
Here's how you’d calculate your required solar panel wattage:
Take your battery bank size (10,000Wh in our example).
Divide this number by the number of peak sun hours where your system is set up (we’ll use 4 hours for this example, even though some areas might get more or less).
Required Solar Panel Wattage: 10,000Wh ÷ 4 hours = 2,500 watts
This means you would need 2,500 watts of solar power to fill your battery bank within one day. In other words, you would need solar panels that have a combined wattage rating of 2,500 watts to charge your batteries in a single day’s worth of peak sun hours.
Remember, solar panels still generate power during non-peak hours, but it's significantly less than during peak sunlight, so it’s always a good idea to ignore these hours while you make these calculations. Think of those hours almost like a bonus where you could potentially generate more power than you need.
Step Three: Sizing Your Solar Panel Array
Now that you know how many watts of solar power your solar panels need to generate, you need to decide how you’re going to achieve that.
Let’s continue our example and say we need to generate 2,500 watts of solar power with our solar panels. Most solar panels available from places like Shop Solar or Signature Solar come in 100W, 200W, or 400W options.
While you could theoretically use a series of twenty five 100W panels, it would be impractical due to the incredible amount of space it would take up. Plus, it’s not the most cost-effective strategy. More realistically, you’ll be looking at picking up 200W to 400W panels.
Panels for a 2,500W Solar Array:
Six 400W solar panels would give you 2,400 watts, which is close.
Twelve 200W solar panels would give you the same 2,400W array.
While these are close to your desired 2,500W array, we always recommend having a bit more capacity to make sure you charge your batteries each day. In either scenario, buying one or two extra solar panels would ensure that you have enough capacity.
The choice between 200W and 400W panels really just depends on your space and budget constraints. The 400W panels are a bit larger and tend to be more expensive, but you need fewer of them. On the other hand, each 200W panel is smaller, but you’ll need twice as many, so they’ll probably end up taking up quite a bit more space.
Other Things You Should Consider
Where and how you are going to be able to position your solar panels is another important thing you need to consider.
Are you mounting them on your roof, on a ground mount, or on top of a van or RV? Each option requires different brackets and mounts, which you’ll need to purchase separately.
Also consider how much practical space you have at your disposal. Just because your property receives a certain amount of peak sun hours per day doesn’t mean that every part of it will. Consider how much unobstructed space you have where you can position solar panels. As you probably guessed, solar panels aren’t going to be nearly as efficient at generating power if they’re shaded by an overhanging tree for half of the day.
Lastly, remember to keep the wattage information handy for when you size your inverter in the next step.
Our Final Words
Sizing a solar panel array doesn't have to be some overly complicated process. By understanding your sun hours, calculating the required wattage, and considering your space and mounting options, you can build an efficient and effective solar panel array.
Also remember not to get discouraged if you can’t afford to build your ideal solar array right at the beginning. You can always start out small and add more solar panels in the future when your budget allows you to do so!
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