How many panels for your residential solar system?

Once we decide to go for solar installation, the next step would be researching about the best solar package for home. The number of solar panels required varies in accordance with the energy consumption of the house. Each KW of solar will produce around 4 -4.5 KWh per day. Size of your system will be this amount divided by your daily consumption. There are numerous other factors that are decisive in choosing the number of solar panels.
• Location – places with more daylight require less number of panels compared to places with lesser day light
• Solar shading – Shading directly affects energy production. Make sure the panels are not shaded by neighbouring buildings or trees.
• Installation – Choose the right panel. Usually tier 1 and 2 panels are recommended.
• Maintenance – Performance of panels depends on how well it is maintained. It has to be dust free for optimum performance.

To calculate the number of solar panels, first we have to calculate the load we have to run. Our average load can be had from our electricity bill. A good solar company helps us in finding the required number of panels for residential solar system.
For the purpose of calculations, let’s say the load is 1000 Watts. Next thing would be to find an inverter that can power your load. If the load is 1000W, we have to go for an inverter of 1600watts. The inverter have to be oversized because DC to AC conversion causes loss of energy. 1600 W inverter comes in 24V.

Power = voltage × current
1000W = 24V × current
Current = 1000÷24= 41.66 amp

So our solar system need to generate 41 amps of current to power the connected electrical load. Size of the battery depends on the backup needed. If we need a backup of 5 hrs:

Size of battery = total load × hours of backup ÷24V
= 1000W × 5 hrs÷24 V

So we need 300 AH, that is 2 batteries of 150 AH.
Sizing solar panels comes last because they need to produce enough voltage and current to charge battery and to run electrical load.
Charging current of battery = 1/10th of total AH
1/10th of 300 AH = 30amp.
So we need 30 amperes of current to feed our battery bank. We have already found that our electrical load needs 41 amp to run. To this we add 30amp that our battery bank is going to take. So 30+41= 71amp.
So solar panels should make 71amp. On an average 250W solar panel makes 30V.

Power = voltage × current
=30V × 71amp = 2130 ~ 2500.

So we need to install panels of 2500W to feed our battery bank and run electrical load. So we can go for 10 panels of 250W each.
It’s an attempt to simplify complex ideas and calculation, though not 100%accurate.

There are many other factors too that decide the number of solar panels. Such as your:

Saving expectation – The number of panels depends upon our expectation from solar system, whether we just need to run our consumption, or we are exporting to the grid or to a battery.
Location – Places with more daylight hours require lesser number of panels than areas with lesser daylight hours.
Solar shading – Shading of panels directly affects the amount of energy produced. So we have to see to it that there is no shading due to neighbourhood buildings or trees.
Installation – Choose the right panels for installation. Always go for tier 1 panels.

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