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Module is one of the important part of the solar PV plant and it should be, because, it is the module which is converter the solar energy into monetizeble commodity, Electricity. So, deep understanding of parameters affecting generating is very important, at least for a Solar PV designer and Solar PV investor Consultant. In this article, I shall take a case study of one parameter, generally facing ignorance by the PV system designer and consultants and that is Tolerance power of solar PV module.

Every module has some capacity in watts and there is a factor called Tolerance power (It is mentioned in %). Module generation capacity is directly proportional to this factor and as this percentage increases, the variability of PV module capacity increases.

 Take a case of 280 Wp module with variability of ±3%, this means module output capacity range is 277 to 283 Wp and in maximum cases, it is on negative side with 277 Wp. And if the tolerance power is 4% that means it is going to give 276 Wp. Techno-financial analysis is presented in this article has been done with the help of PVsyst and financial part is done through simple manual calculation.

As per PVsyst, for a typical solar plant, output generation for a 1MW plant, 280 Wp module with tolerance 3% for a particular location comes out to be 1684 MWh/ yr. Before going further, I would like to mention that for this analysis, I have assumed all other parameter constant except Tolerance so that effect of tolerance can be analyzed.

Now, I have change the tolerance for the same module to 4% and yearly yield reduced to 1644 MWh/ Yr.  Now, it is clearly visible with 1% change incremental change in tolerance reduce the overall generation approximately by 2.5% and figure comes out from the analysis is 40 MWh/ year.

These days solar investor are getting INR 8 or more for per kWh. To make calculation simple, consider cost of 1 kWh solar electricity INR 8. Total financial loss due to 1% increase in tolerance for the typical 1 MW solar project is 3.2 Lac/ year.


By this article, I just want to convey that negotiation is very important while making a solar deal but knowledge of right component will give an edge while making a solar deal and will increase money in your pocket. 

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