It estimates the fuel bill savings you could make and the payments you could receive from the Feed-in Tariff (FITs) scheme. This is to give you an idea as to what financial benefits you may see from a PV system installed in your home.
The calculator assumes that you have a FITs eligible PV installation of up to 4kWp and that you are eligible for the FITs PV tariff indicated in the results. It provides estimates based on the information you provided and a number of assumptions to indicate what scale of financial benefit you could receive; this is to help you decide whether a PV system is for you.
Use of the tool and its outputs is not a guarantee that you will be eligible for the FITs scheme, eligible for a specific FITs tariff or that you will see the exact same fuel bill savings and FITs payments from the installation of your planned system.