The above-detailed calculation is summarised as follows. Let us take 1 kW solar panel (current crystalline panels are 350-400W each) and study the energy it produces in its lifetime. We know that the solar irradiation in tropics is between 5 and 6, we assumed 5.5. That means 1 kW panels produce 5.5 kWh per day . With total system losses of 25% (efficiency of 75%), the 1kW panel produces 4.1 kWh per day for the whole year. The energy produce per year is 1,506 kWh (365 days). Most solar panel manufacturers give 25 years performance warranty showing a degradation to 81% at the end of this period. The average production for this period, therefore, is 90% of the rated capacity. This means that in 25 years 1 kW solar panel produces 33,737 kWh.
If the average cost of power is 7 ₹, then the cost of power produced is 2,36,161 ₹. The cost of a 1 kW solar panel is about 25,000 ₹ and probably another 25,000 ₹ for the system cost. This gives a scale of 10 times comparing cost of energy produced and the cost of the solar panels. We can assume that the energy needed to produce the solar panel is less than 10% of the cost; else the business will not sustain. That implies a scale of 100 times comparing the cost of energy produced and the cost of energy cost consumed in manufacturing solar panels.
A good comparison is to look at alternatives. Solar PV has a 10% carbon footprint compared to coal or oil for every kWh energy produced. A very detailed account of Solar PV can be found in Fraunhofer’s presentation and from the perspective on emissions specifically to Australia in the Andrew Moore article. The energy payback for rooftop PVs shows great benefit.