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Would someone kindly post how to calculate the performance percentage by illustrating some numbers



Hi Alan,

The equation for Performance Ratio (PR) is efficiency achieved by the panels divided by the spec efficiency of the panels (according to the manufacturer's spec). The efficiency achieved can be calculated as the irradiance (solar energy) received by the panels divided by the energy generated by the panels.

Here at the Microgen Database, we calculate the irradiance received by your panels using a method developed in-house, which essentially interpolates from the MIDAS data (Met Office Integrated Data Archive System), and of course we're able to calculate the energy generated using the readings you submit.

The biggest complexity in the calculation lies in calculating the irradiance received, since not only does this require the interpolation of MIDAS data, it also requires a conversion from the total irradiance on a horizontal plane (which is measured by Met Office Stations) to the irradiance in the plane of your panels. There are several methods for doing this calculation, each with different strengths and weaknesses.

Here's a simple example of PR calculation if you assume the irradiance calculation is already done…

Panel spec efficiency (n_s) = 0.15 or 15%

Monthly Generation from panels (G) = 100 kWh

Monthly Irradiance received by panels (I) = 1000 kWh

Achieved Efficiency (n_a) = G / I = 100 / 1000 = 0.1 or 10%

Achieved PR = n_a / n_s = 0.1 / 0.15 = 0.67 or 67%

Hope this helps,

Jamie (SSF Team)


Do you correct for degradation in your PR calculations?

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