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DIY Calculation Guide for 1 kW Solar System

The size of a residential solar system is defined by its peak power. e.g. a 1 kW solar system can produce 1 kW of power per hour on sunny days. kWh stands for kilowatt-hour. 1 unit of electricity implies 1 kW generated/ utilized in an hour. You need to install at least 3-4 solar panels based on watt peak in an array for the 1 kW solar system.

10kW solar systems are a great investment for homes with high levels of electricity consumption or businesses with relatively small electricity needs.

You can calculate your plant size, area requirement and payback period by our DIY guide.

Calculate Solar System Capacity

The first thing to do is to find out how many units of electricity you are consuming on an average monthly. If you’re using 1400 kWh per month, let’s consider an average of 6 hours of sunlight per day, this implies you would need 1400 / 6×30 = 7.7 kW at least every hour, i.e. ~ an 8-10 kW system. If you have an idea of the available area on your rooftop, you can also check out our Solar Calculator.

Let’s understand this by an example. A “10 kW solar system” means an array of solar panels that produce 10 kW for every hour of direct sunlight. So, a 10 kW system, in a location with 4 hours of direct sunlight, makes 40 kWh per day. Assuming 300 sunny days in a year, a 10kw system will generate 14,000 kWh annually which is equivalent to planting 450+ Teak trees and total savings of Rs 45 Lakhs over the lifetime.

Calculate Area requirement for Your Solar System

Parameters which determine the size of the Plant are as follows:

  • Monthly Average Bill Peak load in summers & throughout the year
  • Sanctioned Load
  • Rooftop area or shade-free area

All these points are needed to be analyzed properly as the policies and guidelines of Govt vary state by state e.g. Policies for availing subsidy and Net Metering is different for different states. In Delhi, you can install a system equal to that of the sanctioned load. If you have a sanctioned load of 10 kW, you can install a system up to 10 kW. Similarly, in some states, the maximum capacity of the solar plant allowed is 90 % of the sanctioned load.

For estimation purpose, 70% of rooftop area can be used for the panel’s installation. Certain solar panels in the market can use as high as 90% of rooftop area but have a much higher cost. As a thumb rule, you require 10 sq meter area for a 1 kW solar system capacity. 

Shading is another important factor which decides the positioning and size of the plant. The system should be facing south with a certain degree on the panels. For more details, you may refer to this video. You should look for a maximum area without shade for your solar system to work efficiently.

Calculate Payback Period for Your Solar System

Solar Energy is a renewable source of energy that is revolutionizing the way we generate power. Not just that it is a clean source of energy, but it’s a great investment that adds value to your property with a shelf life of 25 years and it is aesthetically beautiful.

The total no. of years (time) by which the initial amount of money invested for the system will be recovered from the savings made is known as the payback period of a solar system.

Let’s take an example – If you have invested Rs 5 Lakhs for a solar system that gives you savings of Rs 1 Lakh annually, this implies, in 5 years’ time, the profits have paid back your original investment. You can check exact savings in INR from the solar calculator, as explained before. Solar panel price in general ranges between Rs12,000 –  Rs18,000 based on the type of solar panel and capacity in watts.

The solar systems come with a warranty of 25 years. So, while calculating the ROI, the remaining 20 years gives you a profit of 18 – 20 Lakhs considering its shrinkage in performance annually. If we consider the Inflation of 5% in grid tariff annually, (Cost per unit going up to let’s say 5%) we make lifetime savings around Rs 45 Lakhs.

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