Sizing of PV Systems

The sizing of a PV array can be determined by a number of elements that are often driven by the overall aim of the scheme. In refurbishment applications, common motivating factors are to save money and provide energy security; in new build applications, common motivating factors are meeting BREEAM, to save money and provide energy security.

In all instances the system size will be determined by the following considerations:

  • Building Energy Consumption

To ensure the optimal return on investment (ROI), the system should be sized to match the building’s energy profile. The goal is to provide a solution where all the energy produced is consumed by the building. Buildings that are used predominantly during the day such as; offices, schools and factories are perfectly suited to the energy profile produced by a solar array.

  • Usable, Non-Shaded Roof Space

Once shading items and other pieces of plant and equipmen such as rainwater outlet locations, edge protection, maintenance access, mansafe systems, rooftop plant equipment and green roofs have been allowed for the size of the usable space can often be limited significantly.

  • Client’s Budget

Often a project’s financial plan can allow allow for the inclusion of a PV system and capital budget may determine scheme size rather than optimal return on investment or roof size.

Mismatched Expectations

On new build developments, the size of the array will usually be determined by either BREEAM requirements or local planning conditions. This can lead to complications if the size of the output required is not applied to the available roof space to ensure that the system will physically fit on the roof and avoid shading items.