How much Solar PV can be installed on your roof?

An estimate of the potential installed capacity of the rooftop solar PV system must be made during feasibility of the site.

The estimation of potential installed capacity, C_R, in kilowatt-peak (kWp), may be made using the following equation:

where:

• A_R is the total roof area available for installation of solar modules in m²,
  • C_M is the individual module rated capacity in Wp,
  • A_M is the area of one module in m², and
  • RCR is the roof cover ratio, which is the fraction of roof area that the modules will cover.

The roof area (A_R) should be the total area minus the footprint of any obstacles on the roof, such as, water tanks, utility rooms, communication towers, and air conditioning systems, etc.

The rated capacity of the modules (C_M)can be determined from the specification sheets of the modules. These can be easily available from the websites of the respective manufactures.

A typical value for the roof cover ratio (RCR) is 0.8, which would allow for 20% of the roof to be free for spacing between modules and away from obstructions.

Illustration:

Estimated Capacity of the Firstgreen Rooftop PV Project

The Firstgreen team examined the roof plans for a building and found the installable area was 500 square meters. Using specifications of readily available modules (rated at 330 peak Watts [Wp] and sized 1 meter by 2 meter), the initial estimated photovoltaic (PV) system capacity was:

= 66 kilowatts-peak (kWp)