Which system is for me?

The type of system suitable for your property will depend on many factors:

  • Roof type & area available
  • Property location
  • The condition of the roof
  • Your budget

PV Systems Options

ORBS Energy can help you discover the different types of Solar PV Systems suitable for your building. We are happy to help and support you throughout your project whatever stage it may be at or however big it is.
In order to help you decide which type of Solar PV system would be best for you, ORBS Energy has put together a comparison chart covering all of the top options available for use on your project. See our PV Case Studies for examples of these different types of installation systems.


Solar PV System Comparison

Solar PV SystemAdvantagesDisadvantages
Solar PV
  • Can retrofit onto any roof
  • Good value for money
  • The panels are naturally ventilated
  • Generally, no planning permission is required
  • Most efficient type of solar PV system available for buildings
  • Positive visual impact
  • Difficult to get planning permission for these PV systems in conservation areas
  • Look like an add on to a building rather than integrated design
In RoofIn-Roof
Solar PV
  • Integrated with roof and therefore visual impact compared with an on-roof PV system is lessened
  • System lies completely flush with the roof
  • Good value for money
  • Does not require a re-roof
  • More expensive than on roof PV systems
  • The solar panels are still visible and look like solar PV panels
PV TilePV Tile
  • These PV systems are preferred by some planning authorities, no planning permission is required for most areas
  • Easy to fit
  • Reduced visual impact compared with other PV systems
  • Planning permission is still required for conservation areas
  • Expensive
  • Reroof is needed
  • Slightly less efficient than on-roof PV systems
Flat RoofFlat-Roof
Solar PV
  • Can be aligned for optimum orientated and tilt
  • Naturally ventilated
  • Does not require a reroof
  • Efficiency is comparable with on-roof PV systems
  • Always requires planning permission
  • Extra cost due to frame
  • Must be designed carefully so PV panels do not shade one another
  • Extra weight on building from the frame
Stand AloneStand Alone
  • Not limited by roof size
  • Can be aligned for optimum orientation and tilt
  • No roof required
  • Larger PV systems possible
  • Always requires planning permission
  • Extra cost due to frame
  • Electrical trenching is required


Yearly Output

Below is a guide to help you calculate how much electricity a Solar PV system will generate over a typical year. If you would prefer a member of our design team to talk you through this then please call us on 01564 770112


How Much Electricity Will My Solar PV System Generate?

This is known as the Standard Assessment Procedure (SAP) Calculation for Solar PV.
The Government provides a standard method to calculate the amount of energy a PV system will supply over a year.
The equation is:
Predicted Generation (kWh/year) = Irradiance x Shading factor x kWp x 0.8

  1. Shading Factor: Unshaded - 1, Lightly Shaded - 0.8, Moderately Shaded - 0.6
  2. kWp: The kWp is the maximum power of your PV system. It represents the power that would be produced by the panels under standard lab conditions.
  3. Irradiance: Irradiance is the amount of energy that the roof receives from the sun. It depends on roof tilt and orientation, and can be found from the following table.

Yearly output graph


Improving On the Standard Assessment Procedure for Solar PV

The standard assessment procedure is useful - but it gives no idea of how much energy is produced over the course of the year. During summer months, PV panels produce about 5 times as much electricity as in the winter months as the sun is higher in the sky, the weather is clearer, and the days are longer. The graph below shows how the output from a 1.4kWp PV system in Leicestershire, will vary over the course of a typical year.


You can carry out your own assessment for any site in Europe using the online PVGIS tool