How to Calculate the Surface Area Required by Solar Panels

You have estimated the size of the solar system that you need and are ready to get the equipment from the market to install it. But wait, are you sure you have enough space in your garden or your backyard or your rooftop to install the solar panels? How can you do a rough estimate of the area required by the solar panels? Here is a quick and easy way to go about it.

Lets assume that you want to install 10 solar panels rated at 100 Watts each and having a conversion efficiency of 18%. The total power output of the solar system can be calculated as:

Total Power Output=Total Area x Solar Irradiance x Conversion Efficiency

We know the required Total Output Power is 1000 Watts (10 panels x 100 Watts), the Solar Irradiance for a surface perpendicular to the Sun’s rays at sea level on a clear day is about 1000 Watt/m2 and the Conversion Efficiency is 18%.  Plugging these number in the above equation we get:

1000 Watts = Total Area x 1000 Watts/m2 x 0.18


Total Area =   5.56 m2

I you are going to install all the panels in one line you would need a space of approximately 1 m x 5.56 m (each panel having a size of 1 m x 0.556 m) on your rooftop. There you go. You have a rough estimate of the space required by the solar panels of your system.


1. Do remember that solar panels are usually installed at an angle to the earth surface and this may change the results somewhat.

2. Imagine a solar panel has a conversion efficiency of 100% i.e. it converts all the solar energy into electrical energy then all you would need is a 1 m2 solar panel to produce 1000 Watts of electrical energy.

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20 thoughts on “How to Calculate the Surface Area Required by Solar Panels

  1. what is the area required for 25KW plant for south facing arrangement and also give details about battery’s requirement?

    1. Suppose the area is A square meters then the equation becomes.

      1000 x 0.20 x A = 25000

      200 x A = 25000

      A = 25000 / 200

      A = 125 square meters

      This is for panels lying flat on the ground. We would suggest that an area of at least 200 square meters must be reserved due to the following three reasons.

      – Panels are not usually flat, they are placed at an angle and need more spacing so they do not shade each other, depends on your location
      – You might need more panels for achieving peak generation of 25 KW, again depends on your location
      – Panels might not achieve 20% efficiency that we have assumed above (the 0.20 factor that we used above was to cater for panel efficiency)

      For calculation of batteries we need to know the load and the backup hours required. If you want a simplistic answer I would suggest that you put in 50 batteries of 200 AH each for a backup of about 5 hours.

  2. hi,
    total area of roof top is 3000 metre squre .i need 30000 KW power consumption per month.almost 2000 kw per day consumption.could you please give me the desighn data for solar panel.
    we need
    1) maximum amount of kw produced for one metre squre panel and the cost of one metre squre panel

    2) finally we need 2000 kw per day please give the sample calculation .

    1. Suppose you have A meter squared of area. Then you can generate

      A x 1000 x 0.2 Watts of power

      Set this equal to the required power of 2000,000 Watts

      A x 1000 x 0.2 = 2000,000

      => A = 10,000 meter squared

      So the area you have 3000 square meter is not sufficient to produce 2000 kW of power.

      One square meter can produce about 200 Watts and the cost of the solar system is about $1 to $2 per Watt depending upon how much backup you want. Solar panels can produce peak power for about 5 hours daily.

      With the area you have you can produce 3000 x 200 = 600,000 Watts (600 kW) of peak electric power.

      Lastly power is in Watts and monthly generation of energy is in KWHr, so please be careful with calculations.

  3. I want in install solar panels in 2000 square meters. I wish to know how much it will cost to install solar panels and the cost. How much electricity can be produced.

    1. 2000 sq meters means you can capture 2000 x 1000 x 0.15 = 300 kWatts of solar power. In one month you can produce 45,000 kWhr of solar energy. Cost of the system depends upon a number of factors and can range from about $1 to $2 per Watt.

  4. Hi
    1280 sq feet= 118 sq meters.
    What is the capacity of plant in Andhra Pradesh, India.
    I would like to supply total to the discom company. Is it require for storage plant.
    What is the total cost?

  5. hi
    this is my requirement.

    Sr. # Product Units Wattage Total Watts Daily Usage Total Watts -hrs
    ( Hrs)
    1 DC fan 12 36 432 6.00 2,592
    2 LED Lights 12 12 144 6.00 864

    how many solar panels required, battery size and charge controlers size

  6. hello plz help me to improve my knowledge for solar panel how can calculate power ,current and voltage and erea so plz help me am Eric from Rwandese student in Mechanical Engineering

  7. Derek you are right. These calculations are not exact. But sometimes you need quick “back of the envelope calculations” to get a rough idea.

  8. Your calculations assume the panels are always producing 100W, which they won’t since they don’t track the sun and the location of the panels on the earth isn’t given either which can greatly effect a panels output.

  9. Hello!!! I have a doubt. If I need the solar that provide 500w. How many areas of solar panel that I use? And how to calculate it?

  10. Roof size 2000 sq ft. Can you please mail me the max capacity of plant work on it, and total cost after subsidy for ongrid plant.

    1. 2000 sq ft = 185 sq meters
      185 sq meters x 1000 Watt/sq meter x 0.20 efficiency = 37 kilowatt
      That is the plant can produce a maximum of 37 kilowatt during peak radiation around noon time.
      The cost can be approximated as 37000 Watt x $1/Watt = $37000 = 2.5 million Indian Rupee.

  11. Hi
    I’m UG student, doing my final year project, we have 30KW power, for this wattage how many solar panels are required and also how to calculate the area?

    1. You will have to make a few assumptions. Lets assume that you have 100 Watt panels. You will need 300 of these to generate 30 kW. To calculate the area you need to know the efficiency of the solar panels. Lets assume the solar panels have 20% efficiency so the energy produced is 200 Watt/m^2. So the total area required is 30,000/200 = 150 m^2. This is assuming that the panels are placed on a flat surface along the ground. Keeping some margins you can say that a 15 m x 15 m area would be sufficient.

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