How Many Solar Panels Do I Need?

How many solar panels do I need?

It seems like a simple question, but there are a lot of considerations when deciding how many solar modules (commonly called solar panels) you need to power your property.

Some of the factors that decide the number of solar panels you need are: 

  • The average annual electric usage of the property (or projected usage for new properties)
  • Efficiency and size of the solar panels purchased
  • The sun's irradiance (power) in your geographical location
  • The direction and angle the solar panels will be positioned in
  • The amount of space available to host the solar panels

Annual Electric Usage

One of the biggest factors in deciding how many solar panels you will need is your electrical usage. The more energy you use, the more solar panels you will need to power your property. Most people are unaware of how much energy they use, and that's not a problem! We use your last twelve months (or more) of electric bills to find out your annual average electric usage. 

The Sun

The sun's irradiance (power) changes depending on your location. How far you are from the equator, your hemisphere, and a few other factors can affect the total sunlight you receive.  As a rule of thumb, the more sunlight you receive, the more power you will generate. If you are in a location with less sunlight, you may require more solar panels to make up the difference.

The Solar Module Type

Solar modules themselves vary drastically in their materials and efficiency. For example, monocrystalline solar panels are more efficient than polycrystalline. Higher efficiency modules mean you'll need less of them to produce the same amount of power.

On top of that, solar modules commonly come in two sizes: 60 cells and 72 cells. Solar panels that are 72 cells are larger and give you a better value, while 60 cells are smaller and can fit into tighter spaces.

This is especially important to consider when you're comparing quotes from solar companies. While one quote may be cheaper, it could be because they're using less efficient modules. This may be cheaper upfront, but it will result in less savings because your array is producing less electricity.

Available Space

Available space is a major factor when considering how many solar panels you need. If you're in the Northern Hemisphere, then solar panels should face south to receive the most sunlight so they can generate the most energy. If your solar panels are placed on an East or West-facing roof, you'll need a few more modules to equal the production you would get with a south-facing roof. 

While roof mounted solar arrays are what most people picture when envisioning a bright, shiny solar array, you may need to consider a ground mounted solar array if your roof needs to be replaced, is shaded, or is too small. Ground mounted solar arrays are installed facing South and at an ideal angle, which helps ensure they maximum energy production (meaning a lower electric bill for you!). 

Both roof and ground mounted solar arrays require unshaded space to be installed. Some shading may be permissible, but we always recommend removing obstructions. Shading heavily affects a solar systems efficiency, and we want you to get the most out of your solar system. 

As NABCEP certified solar installation professionals, we take these factors into account when generating your solar quote. This way, we can ensure that your array is designed to meet your specific needs and saves you as much as possible. 

Tags: solar panels production panels

Janae Rowe

January 9th, 2019


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