In the previous article, What is the average cost of solar roof in India ?, we learned that the average cost of the solar roof in India is Rs. 83 /watt to Rs. 91 / watt (without battery back up). Now let us determine the Payback period and the financial feasibility of the project. The Payback period is the time required to cover your initial investment made in purchasing and installing the solar roof at your residence. We will determine the financial feasibility of the project through Net Present Value method, which is done by summing all the future savings after discounting them to the present value and subtracting the initial investment. The following is the stepbystep procedure, which tells on how to determine the payback period and the feasibility of the solar roof: The Average cost of 1 kW Solar RoofHere we are assuming that you have installed 1 KW system at your roof top which costs you in between INR 83,000 to INR 91,000. You can get the cost for the higher wattage like 2 KW or 3 KW by simply multiplying it by average cost per watt, which is Rs. 83/watt – Rs. 91/watt The Peak Sun Hours in a DayYou can find this data from the official website of renewable energy of your state. The average number of daily Peak Sun Hours in India are 5.5 Units generated by the systemYour 1 kW system will generate 1 kW x 5.5 Peak hours = 5.5 kWHr or 5.5 units in a day under ideal conditions, assuming that there will be no energy conversion losses and heating losses. Actually, there are certain losses which reduce your output power. The significant factors that reduce the efficiency of the solar panel are as follows:
All the above factors affects the efficiency of the system. Finally, 1 kW system in India gives around 3.5 units in a day instead of 5.5 units. Understanding the performance of your solar panel When you purchase the good quality solar panel, the manufacturer provides you the performance warranty on it. The performance of the solar panels reduces gradually over its lifetime of 25 years. Your 1 kW solar system in India generates the electricity units in the following fashion: Average rate of electricity in IndiaThe electricity that you receive in your houses from the grid comes at a cost, which is generally expressed as the rate per unit consumed. The rate of the units consumption is divided into slabs. The average rate of electricity increases with the increase in the consumption of units. This is something against the law of economies of scales :)
Maintenance cost of the systemYour system will need maintenance, after installation, on regular basis. The maintenance process will involve the following activities:
During initial years of operation, the cost of maintenance will be less and afterwards it will start increasing with the age of the system. The solar system without battery backup doesn't require much maintenance hence the maintenance cost is low, somewhere around 05.%  1% of the cost of the system per year. The cost will not remain at Rs. 5/unitBy looking at the past trend, the average rate of the electricity is growing at the minimum average rate of 5% per year. It means we will be paying Rs. 16 for the same unit consumed at the end of the 25th year. Please have a look: The payback period of the system
Therefore, to get the more realistic value of your solar roof, we need to calculate the Net Present Value of the future savings or income generated by the solar roof. The Net Present value
The complete feasibilityThe features of 1 kW Indian residential solar roof are as follows:
As you increase the wattage of the solar roof:
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