How to calculate the sizing of solar panels for home

When installing solar panels on your roof, it is essential to assess the sizing of solar panels. Size plays an important role in designing a solar system for maximum energy generation and conservation. 

An assessment of the sizing of solar panels can also assist with a better installation, which in turn improves performance and efficiency. Sizing the solar panels can sometimes be tricky. We have outlined below a thorough 7-step process that can guide you through the business of identifying the right size of panel that meets your every requirement.

6-Step Guide to the sizing of solar panels

  1. Selecting the PV module

When selecting a PV module, some factors to be considered are technology, cost, availability, warranty, efficiency, and service support. 

The technology is of two types: mono or poly panels. Poly panels are generally more affordable than mono panels. People, thus, often choose poly panels, especially when space availability is not an issue. 

On the other hand, with an efficiency of 19-20% mono panels perform better than poly panels which have an efficiency of 16-17%. If there’s a shortage of shadow-free space on your rooftop, then mono panels are the way to go. 

The selection of PV modules also depends on availability. Did you know that even if the panel is assembled in India, the PV cells required to make that panel come from China? Hence, keep the availability factor in mind when choosing a solar panel for home. 

  1. Calculating the number of modules

The number of modules can be easily calculated in the following manner:

Say you have a module of 350 Wp and you want to set up a 10 KW solar system, here’s what you need to do: Divide the capacity of the solar system (in watts) by the capacity of the module. 

In this case, the total number of modules = 10,000 / 350 = 28 

The requirement is, thus, 28 modules in the sizing of solar panels in this case. 

  1. Selecting an inverter

The inverter selection follows the same process involved in selecting the module. As with the module, you can choose an inverter based on cost, efficiency, availability, technology, service support, and warranty. For inverters, there are two technologies available – string and micro. 

String inverters have a direct connection to the grid and are commonly used for commercial and residential purposes. Microinverters, on the other hand, are smaller and costlier than string inverters. But their cost is justified in terms of efficiency.

You can select the inverter that best suits your home’s needs.

Calculation of the number of inverters 

Assuming that the selected inverter is 2500 Wp and the total required wattage is 10,000 watts (10 kW), then, the total number of inverters required would be 10,000 / 2,500 = 4

Hence, in this case, For the sizing of solar panels for your residence, you would need four inverters.  

  1. Calculating the string size

The string size of inverters can be calculated using software; however, there is some information that you will need beforehand. This information includes the Voc of the PV module, Mppt range of the inverter, Vmp of the PV module, and Vmax range of the inverter. 

Once you gather this info, it is simply a matter of using the appropriate software to determine the string size you will need for the sizing of solar panels for your house.

  1. Selecting the mounting structure

The mounting structure has to be selected based on some factors, such as the type of roof structure, snow/wind load, type or tilt of mounting, type of environment, structure material, and cost. 

  • – Mounting structures are of different kinds and classes, such as fixed tilt, flush mount, ballasted solar structure, single-axis tracking, and east-west racking. 
  • – Also, when choosing the mounting structure, it is necessary to focus on the tilt. Generally, the ideal installation method is such that the panels should stay near-perpendicular to the sun between peak sunshine (between 11 AM to 2 PM). 
  1. Simulation

The last step of assessing the appropriate sizing of solar panels is simulation. Simulation software assists engineers in improving the design of your solar system, particularly concerning shadow analysis.


The aforementioned 6 steps offer a clear idea about the calculations required to assess the sizing of solar panels for your home. The calculations will, of course, vary on a case-to-case basis. However, the main aim remains the same: sizing of solar panels in such a way that all your power requirements can be met with electricity from solar.


How do PV panels work? 

Now that you know all about the sizing of solar panels, it’s also relevant that you understand their basic functioning. 

It’s simple.

Solar panels absorb sunlight between 9 AM to 4 PM and convert it into direct current (DC). This DC electricity passes through an inverter to be converted into usable AC electricity. Surplus energy is transferred to the grid in the case of an on-grid solar system

How do you select a PV module?

PV modules are of two types- poly and mono, of which the former is more affordable, bulkier, and less efficient but readily available than the latter. Thus, you will have to decide which PV module fits your particular needs.

What are mono and poly solar panels? 

Mono or poly panels are both PV panels that are used to convert sunlight into electricity. However, how they are manufactured is different. 

Monocrystalline solar panels are made with one single crystal of silicon; hence, their efficiency is on the higher side (19-20%).

On the other hand, polycrystalline solar panels, also knoware made up of multiple crystals of silicon. Which is why they’re also known as multi-crystalline panels. Their efficiency is about 16-17%, that’s lower than that of mono panels.  

How are modules distributed amongst the inverters in a solar system during the sizing of solar panels?

This can be done through a simple calculation. Divide the number of modules by the number of inverters in your system. Voila! You have the number of modules required per inverter during the sizing of solar panels. 

This calculation is just a guide. During the actual installation process, you may have to vary the numbers for practical reasons.

What is the maintenance cost of solar panels? 

Solar panels are not high-maintenance products. The AMC contract will always cover basic maintenance requirements as long as you’ve purchased a tier-1 module from the right brand. The premium-quality modules have a life of a minimum of 25 years.