Solar ROI is the first free independent tool, which calculates the payback period of solar panels without commercial involvement. R.O.I. stands for the term return on investment.
ROI = income per year / investment

With Solar ROI you can compare tenders and the higher the ROI, the sooner you have recouped your investment. However, the payback time in years is dependent on several factors. In a project, you should compare the result with the situation while you are doing nothing. If you would not buy solar panels, would you leave your money on the bank and receive interest or will you spend it for something else? In the first case, you may also have to take in account the property tax, which you have to pay in some countries.

Or would you rather take an additional hypothec on your house to fund your solar panels. In some countries, you may deduct the interest from income tax. The first choice you have to make in the App is whether you will invest as an individual or as a company. The next choice is whether you fund your investment through savings or are you going to invest through a hypothec or loan.

The app instantly calculates ROI with some default values for savings, hypothec or loan, but you can change the settings for 'Savings', 'Hypothec' and 'Loan'. Then enter the required budget. You can request estimates from suppliers of solar panels..

The results can be shown in a table or a graph. The tool is not a black box and all calculations are displayed in datasheets and graphs.