Did you know the average residential solar system size today is around 20 to 25 solar panels? However, the exact number of solar panels required to power your house may be higher or lower. It all depends on your home and your individual power needs.

Considerations When Finding the Number of Solar Panels for Your Home

Let’s look at various factors solar panel installers consider when calculating the optimal quantity and size of residential solar panels.

Your Home’s Energy Consumption

To completely power your home with solar panels, you must first determine how much energy your household uses in a year. After all, you’ll need enough solar panels to hit that threshold. You can see how much energy you’ve used by looking at your utility bills for the year.

The Solar Panels’ Rating

Solar panels come in various power ratings depending on their size and material. The power rating refers to the panels’ watts per hour if exposed to sunlight on a clear day. The higher the power rating you choose, the fewer panels you’ll need to install. Most residential solar panels come in power ratings ranging from 250 to 400 watts.

Hours of Sunlight in Your Location

Since solar panels rely on sunlight to generate energy, you’ll need to determine how many hours of sunshine your area has on average. The more sunlight your home gets, the more power your panels generate.

Panel and Roof Size

The size of the roof and the panels you choose also affect how many panels you can install. If you have a small roof, you might need to get smaller panels with higher power ratings so you can install enough to power your home fully. But if you have a large roof, you can go for larger panels and panels with lower ratings.

How to Estimate the Number of Panels You Need

Before we start calculating, we’ll need the following values:

  1. Determine Your Energy Usage: In our example, let’s say your household consumes 12,000 kWh of electricity in a year. That would mean you use nearly 33 kWh per day. 
  1. Decide on the Solar Panel Rating You Want: We’re going with panels that have a 300-watt rating for our example. 
  1. Get Your Area’s Hours of Sunshine: For the numbers below, we’re assuming 5 peak sun hours a day. As we mentioned above, your figures will vary based on your home layout and the area where you live.

To determine how much power one panel will generate, let’s use this formula first:

Power rating (300-watt rating) x Hours of sunshine a day (5 peak sun hours) = Energy generated by the panel in a day (1500 watts or 1.5 kWh per panel)

In our example, each panel produces 1.5 kWh.

Afterward, we use this formula to determine how many panels you need to generate 33 kWh (or however much you consume daily):

Daily kWh consumed (33 kWh) / kWh generated per panel (1.5 kWh) = Number of panels needed (22 panels)

Your home would need 22 300-watt solar panels to generate 33 kWh every day. Those 33 kWh a day would add up to 12,045 kWh a year—enough to meet your energy demand of 12,000 kWh. The solar system’s size would be:

Power rating (300-watt rating) x Number of panels (22) = Solar system size (6,600 watts or 6.6 kWh)

So in this case, we’d recommend a 7 kWh system to fully cover your electricity needs, just to cover any unusual peaks.

But as mentioned earlier, you also have to consider your home’s roof size. The average solar panel size is 5.4 feet x 3.25 feet or 17.55 square feet.

The square footage of each panel (17.55 square feet) x Number of panels needed (22) = Square footage needed to accommodate the panels on the roof (386.1 square feet)

If your roof doesn’t have enough space, you might need panels with higher power ratings, which means you’ll install fewer panels. 

Determine Your Residential Solar Panel Size with Design 1 Solar

While online tips and facts about the average residential solar system size can help you get a rough estimate, a professional solar panel provider can provide the most accurate figures about what works best for your home. Design 1 Solar Group has a team that will meticulously study your property, location, and energy consumption to develop a solar system design that fits your needs.


If you’d like to learn more about going solar, check out our blog or contact us anytime!

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