If you are reading this, chances are you’ve already made up your mind about going solar and are currently looking into the details of a solar system installation. Well, welcome to diving deeper: today’s topic is the size of your PV system.

How many solar panels do you need?

This seemingly simple question is not an easy one to answer. By googling for an average solar system size estimate, you will most likely see different numbers ranging from 6 to 30 photovoltaic panels (with typical residential panel dimensions of about 65 inches by 39 inches or 5.4 feet by 3.25 feet). You probably wonder how to understand this large scatter. So how many panels are necessary – 6 or 30?

Firstly, photovoltaic panels are quite similar to any other device and vary in how much solar energy they can produce. This is called a power rating, with a typical panel generating between 250 and 400 watts. The second and even more instrumental factor determining the number of panels and the size of your solar system is your energy requirements. In the next section, you’ll learn how to calculate this size.

Calculate how much energy you use (and discover how big your solar panel system should be)

To determine your home’s average energy needs, check your past electricity bills and look for kilowatt-hours (kWh) used. A kWh equals the amount of energy you would use by keeping a 1,000 watt appliance running for one hour. Take the total kWh on your electricity bill and divide it by the days the bill covers.

For example, if your average monthly energy consumption is 124 kWh, you need about 4 kWh daily. This is the amount to be produced each day for your solar system to be effective. If the weather is sunny, 4 kWh in a day can be generated by a 1 kW system, which is a small size. 1 kW of solar panels equals 3 panels each of 330 watts.

According to some statistics, a 5 kW solar system is the most popular size of solar panel installation you can see on domestic rooftops. A system of this size usually has 15-20 panels and can produce 20 kWh in one day. For big houses, a 6 kW solar system is the perfect size (it comprises 24 panels and produces approximately 24 kWh within a day).

How much solar power can you get?

Two essential factors that limit the size of a solar system you can add to your house are the space needed for solar panel installation (either on your roof or on the ground) and your budget.

Space available for solar panels

The place you chose for your solar system installation must comply with several criteria:

  • Photovoltaic panels work best when there is no shade cast upon them. Other buildings, trees, or hills, can block incoming radiation.
  • The installation place must be free from obstructions. Obstructions can come from any direction and may include vents, satellite dishes, chimneys, skylights, etc.
  • In the northern hemisphere, photovoltaic panels should face true south (and in the southern, true north).

How much solar can your roof handle?

For a roof-mounted solar installation, each panel needs an area of approximately 18 square feet. For instance, let’s take photovoltaic panels that produce 280 W. Therefore, 1 kW (1000 W) of installed panels will need a roof space of about 65 square feet size.

What space is optimal for ground-mounted solar panels?

Ground-mounted panels need an area of a larger size than rooftop panels, especially if there are multiple rows, because we have to account for shading created between the rows. For example, for a south-facing solar system tilted to 30 degrees (to optimize power generation), the effective area needed by the panels would be around 60 square feet for the same 18-square-foot panel.

Budget factor

On average, solar equipment and installation can cost from $15,000 to $25,000, according to the latest information from the Center for Sustainable Energy. The more powerful the system is, the higher the price. But keep in mind that this is the cost before any tax credits or incentives. If you purchase a 5 kW system that costs around $15,000, you will get a $4,500 credit (30% of $15,000), with the Federal Solar Tax Credit, your solar installation would end up costing only $10,500.

The cost of your solar energy system depends not only on its sizing according to your energy needs but also on the equipment you choose – it is up to you how to handle it. You can choose either a premium brand or a more affordable option.

Do you need help with solar panel system sizing?

First of all, it should be mentioned that there are a variety of online tools, many of them available for free, that can be used when you don’t know how to size and design your solar energy system.

Another way to determine the size of your solar system is to ask your solar installation company to do it for you. Solar providers can combine available online tools with a personal assessment of your needs to develop the most accurate projection of photovoltaic panel output. A reputable company would not refuse to provide a free quote for you to consider.

Key takeaways about determining the size of your solar panel system

  1. To size your solar panel installation properly, determine how much solar energy your home needs.
  2. Look into your electricity bills to find out how much energy you consume daily.
  3. A 5 kW solar system is usually adequate for an average American home.
  4. If the area does not receive a generous amount of direct sunlight, your solar system may not be able to produce enough energy.
  5. If you are on a tight budget, you need to decide the size of your solar system depending on how much money you can spend. Search for a cost-competitive solution and explore available incentives, either on your own or with the help of a solar professional.



Apr 3, 2023

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