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Solar Photovoltaic (PV) Calculator

It’s important to know the facts about solar panels before you make the decision to invest in them. You can use the solar PV calculator below to calculate estimates for how much you could receive from a system of solar PV panels. Whilst the figures provided by the solar PV calculator are only estimates and cannot be exact, the solar PV calculator is a good way to give yourself an idea of your savings and how much you will earn from your Feed-in tariff payments.

The results from the solar calcuator is often referred to as SAP calculations. Once we have carried out a survey of your property we will provide you with accurate SAP calcutions which take into account:

  • the actual size of your solar panel system (measured in peak output or kWp)
  • the pitch of your roof eg 40 degrees
  • the aspect of the roof, eg south, south west etc
  • any shading from trees or other buildings.

How to calculate the size of your solar panel sytem from your roof area

Most solar PV panels are around 1.6 meters high and 0.8-1m wide, each producing 175-250W of electricity (depending on the type and effeciency). Therefore to produce 1kW of solar panels you will require between 8 and 10 square meters of roof space for 4-6 panels. When estimating the size of your solar panel system we allow 10m2 per 1kW, because the installer needs to leave around 0.3m of space at the edges and below the panels.

You will need to measure the size of your roof in order to calculate the avaiable area in square meters. You can either get out the tape measure or use Google Earth to get an idea of the roof size. For example if your roof is 5 meters wide and you estimate that it is 4 meters to the ridge, then your roof are will be approximately 20 square meters. Once you have calculated your approximate roof area then you need to devide this by 10, to calculate the size of your solar panel system in kW. If you have 20 square meters then you will be able to have a 2.0kW system.

Currently 3.68kWp is the maximim size for a domestic system, due to limitations in the amount of electricity you can import into the grid. Commercial systems with 3-phase electricty can import 3 times this without requiring any special permissions (G59) form your energy company.

For more information about investing in Solar PV panels, fill in the form on the right, or contact us on 0116 2987467.


Solar PV calculator provided courtesy of Solar Guide.

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