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Calculation of Photovoltaic Performance in Excel
September 30 2011

Calculation of Photovoltaic Performance in Excel

IONIKI offers you a program for calculating the performance of photovoltaic systems in excel. With this program you can calculate the profits of the investment in photovoltaic systems, taking into account the bank interest rates, the security-maintenance costs the desired repayment years of the loan.

You can download the program by pressing HERE. To be able to use the program you need office excel 2007-2010.

In this program you can input some data to calculate the performance of your PV system.

fotovoltaiko excel screenshot


Data input

First of all, select from the box below the year in which you plan to conclude your contract with the DEI.

As is well known, the kWh for contracts to be signed until 01/08/2012 will be € 0.495, and each semester will be reduced by 5%. More about new prices can be found here.

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Just below the year of signing the contract you write the desired installed power of your system (in kW).

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In the cell "Συν. Κόστος σε ευρώ" you write the amount of the PV system without VAT.

If you are going to install the system with your own funds then the value "0" is entered in the "Financing%" cell. If you are going to be funded by a bank, you place in that cell the percentage of the total capital you will get as a loan from the bank. In this case, you should also fill in the "Interest Rate" cell with the interest rate proposed by your bank.

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The "VAT" cell your enter the value of the current VAT. (currently 23%), while in the "Έτη αποπληρωμής" cell enter the years for which you are going to receive the loan. Typically, loans for PV systems have a repayment time of 8 to 12 years.


The following table will show results on an annual basis for the 25 years that the contract with the DEI will take effect.

fotovoltaiko excel screenshot

So we see for each year of operation the total revenue that the system brings us.

Of these, we deduct some typical maintenance and insurance costs (which is optional) and earnings remain.

If the investment was made with own funds, the profit of each year is added to that of the previous one, so we have cumulative profits for the entire 25 years.

If we have received a loan from a bank from the profit we will have to deduct the installment of the loan and the interest for each year.

The chart shows cumulative cash flows throughout the 25-year period. In the case of investing in own funds, we can very easily discern the year in which the depreciation has taken place. (Where the bars are passed to positive values)

In the case of 100% funding, we have not put capital, so cumulative cash flows start from scratch. We just accumulate the excess amount each year after deducting the installments of the loan and the interest. In this case, from the chart we can conclude that from the year when the loan will be repaid, profits will increase much more rapidly.