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May 12, 2021 | Solar Panels

How Many Solar Panels Do I Need?

Written by Madelein Kroukamp

Going solar is not a one size fits all kind of deal. Determining how many panels you will need is quite complex, there are a few factors to consider when trying to figure out how many panels you will need to generate enough power for your requirements. These factors are:

  • Electricity output desired
  • Sun-hours availability and inefficiency factor
  • Specifications of the solar panels used

Let’s have a closer look at these aspects.

Electricity output desired

The first step you need to take when determining how many solar panels you would need is to calculate how much energy you use. In other words, how many kilowatt-hours (kWh) of electricity do you consume in an average month? It will be helpful to make sure your house is energy efficient before doing this. Most homes use more electricity during certain times of the year, so calculating an average is more accurate. Ask your municipality for your utility bill for the last 12 months and work out the average kWh you use per month. Your kWh requirements should level out with the kWh produced by your solar system.

Sun-hours availability and inefficiency factor

Your sun-hours availability is not the same as the hours the sun is shining. Peak sun-hours are when the maximum amount of power is being generated when the sun’s rays shine directly on the solar panels. Too much shade will diminish your capacity to generate power, leading to you needing to use more panels. Your panels should also face northwards to optimize sun availability. 

Some factors affect the efficiency of solar panels, influencing the amount of power being generated. These include temperature, geographic location, the orientation of panels, and shading.  

Specifications of the solar panels used

When using solar panels of higher quality that can generate more energy will have a direct effect on how many panels you will need. Polycrystalline panels are the most commonly used, being of good efficiency and reasonable price. A panel generates between 275W and 350W. According to Eskom, the average home in South Africa uses over 30 kWh per day if they are not efficiency conscious. 

By doing a quick calculation, you can more or less figure out how many solar panels you will need once you have determined all the above-mentioned factors. 

kWh used per day ÷ sun-hours ÷ 0.9 (inefficiency factor)

This will give you the number of Watts your system should be able to generate. This amount should then be divided by the number of Watts your individual solar panel can produce (this information should be available to you when purchasing).

Determining how many solar panels you will require to generate sufficient power to meet your requirements is not a simple task. Especially with so many factors that have to be considered. Therefore, it is important to consult with a solar system engineer and installer. They will give exact calculations and you won’t be left in a pickle due to wrong estimations. 

Thank you for reading this article. If you feel we have left out any important information or would like to contribute to this site and content, please get in touch with us by leaving a comment or emailing us.

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