Consider the performance degradation of solar panels when calculating annual yields
The rooftop solar markets are expanding rapidly in India. On the back of government incentives and reducing solar prices, the number of installations is expected to go up significantly in the coming years in the light of the national goal of 40,000 MW by 2022. A number of solar vendors are marketing solar panels to the roof owners with the promise that solar panels will last for more than 25 years. Yes, the life of panels is quite long, of course, but there is a certain performance degradation observed in the generation from solar panels. The degradation in the performance of the solar panels varies typically with the material of the panel as well as depending on the weather conditions in which they operate. The generation degradation is observed much more in the Thin Film technology vis-à-vis that in the Crystalline Silicon technology.
In India, the solar photovoltaic markets are dominated by Crystalline Silicon technology. Over the life of a panel of 25 years, these panels can see a degradation of 4- 5% in its output. This degradation would be higher and could be double for the Thin Film panels. As per the lab tests in Indian conditions, the Crystalline Silicon panels tend to have higher degradation in initial 4-5 years than that in the later years. The PV installations also have higher degradation in high humidity conditions and also witness some wear and tear due to various reasons; for example, it is slightly higher in Rajasthan.
It may be required to replace, say, 5% of the total panels which are especially nearer to high voltage side in the beginning of the array. Therefore, some capital expenditure, say, upto 5% of the CAPEX for panels may have to be incurred on retrofitting at the end of about 10 years post- installation.