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How big solar energy system do you need for your house in India?

How many solar panels do i need

If you plan to install the solar system on your roof to reduce the electricity bills and carbon emission then the most common question first comes to mind is How many solar panels do I need? and everyone gives only one answer it depends on use and available area.

This is the very common question because most people want to reduce their electricity bills by producing the energy through the solar system. Determining the how many solar panels you need the first you should know some following:

1.) How much electricity is used by your household?

2.) How much shadow free space you have?

Let’s see:

1.) How much electricity is used by your household?

 

To determine the solar energy system requirements look at your past electricity bills. You can find how much average electricity is used by your house the bills generally in Kilowatt-hours (KWh). You can also find by using the meter reading just take bills and note down ending reading and subtract from recent month ending reading.

You need daily consumption so divide monthly energy consumption by no. of the day you can find your daily consumption of energy. And your daily use of energy will decide how many solar panels you required if you go 100% on solar.

2.) How much shadow free space you have?

 

The meaning of shadow-free space is how much free area you have in south or southeast or southwest orientation and without having any nearby building and trees which create the shadow.

You will need 10 Sqm. for installing the 1 kW solar. If you do not have much space then you can go for alternate installation option like elevated structures but its need to check the feasibility of your roof and the strength of the structure.

You can check alsoBEST PRACTICE FOR DESIGN OF SOLAR PANEL MOUNTING STRUCTURE

In other hands, roof orientation is also the factor, in India solar panel work best in south direction and panel in the south-east or south-west is in also used.

How many no. of solar panels will fit your roof?

 

Ones you know above two points how much electricity used and shadow-free area available. Then you need to go find out the how many no. of solar will fit on the roof.

So let’s take an example:

Let’s say you have 900 Sq. ft. open and available shadow free areas and its orientation is south. As shown in below image.

How many solar panels do i need

In below image a space which is 30 Ft. in length and width whose total area is 900 Ft. and also have the peripheral wall (parapet wall) whose height is 2 Feet. Follow some steps to see how many panels will fit.

1.) you know that available area has peripheral wall height 2 Feet. When the sun travels from East to West then cast the shadow on the roof.

So avoid the shadow will consider setback around 1.5 times of height. This setback is also good for maintenance during the operation period in 25 years life.

Then setback = 1.5*2 = 3 Ft.

Let’s say 900 Sq. Ft. areas after considering setback = 729 Sq. Ft. (it means Approx. 80 % is used for solar panels)

2.) As you know the available area is 729 sq. ft. then we should go for the solar panel area.

Let’s consider solar panel dimension = (6.4 ft. x 3.2 ft.), the area of the panel is 20.48 Sq. Ft.

Then divide total available area by solar panel area = 729/20.48 = 35.5(approx. 35 no. of the panel.)

3.) The solar panel power is considered 300 Wp

Then multiply no. of the panel to power watt peak = 35*300 = 10500 Wp (i.e. 10.5 kW)

Hope you will understand the calculation to find out no. of the solar panel.

How much energy will produce by the solar system?

 

Nowadays many online software is available where you can simulate your solar system and you will find how your system will perform over the period and how much energy produced.

I have mostly used PVsyst and PVWatt calculator. You can use PVWatt its online toll and free by NREL.

Now here I am showing you the example of the generation of PVWatt of the solar system.

You need to follow some steps to generate the PVWatt result.

1.) First, feed your location. For example, I have feed Pune.

How many solar panels do i need

2.) Then go and next page you will find as shown in below image.

How many solar panels do i need

3.) Then click Go To system info you will find the new page as shown in below image. Fill out the data of your system.

How many solar panels do i need

I have considered the following:

DC system size = 10.5kW

Module Type = Standard

Array type = Roof

System loss = 11 % (you can also take 11 % for safety generation result)

Tilt = 20° (You can consider tilt is equal to your location latitude)

Azimuth = 180° for south direction

4.) Go to PVWatts® results you will find the result as below image.

How many solar panels do i need

Here you can see10.5 kWp Solar system is generating 16758 kWh/Year.

Now you can download this generation monthly as well as hourly as you wish. And you can compare what is your monthly electricity bill of the house and what size of solar panel you required to reduce the electricity bills.

 

Thanks for Reading.

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